2022/36 “Cambodia-Vietnam Relations: Key Issues and the Way Forward” by Kimkong Heng

Cambodia’s Prime minister Hun Sen (L) shakes hands with his Vietnamese counterpart Nguyen Xuan Phuc (R) prior to a meeting at the Government Office in Hanoi on 4 October 2019. Picture: Nhac NGUYEN / AFP.


  • In recent decades, Cambodia and Vietnam have enjoyed strong and deepening bilateral ties, but their relations are not without contention.
  • The unfinished demarcation of their land border has caused persistent disputes between the two countries. This has not only shaped Cambodia’s domestic politics but also contributed to the lingering suspicion among certain Cambodians about Vietnam’s expansionist intentions.
  • Ethnic Vietnamese immigrants in Cambodia remain a long-standing problem that has been exploited to fuel nationalist and anti-Vietnamese sentiments in Cambodia.
  • Popular views on Vietnam’s role in Cambodia, particularly regarding its liberation of Cambodia from the Khmer Rouge regime, have been highly divisive, creating tensions in Cambodian society.
  • Cambodia needs to work both independently and collaboratively with Vietnam to find ways to resolve these important issues to ensure healthy and sustainable Cambodia-Vietnam ties.

*Guest writer, Kimkong Heng, is Visiting Senior Research Fellow at the Cambodia Development Center and an Australia Awards scholar pursuing a PhD at the University of Queensland, Australia. The author would like to thank Mr. Sovinda Po for his comments on an earlier draft of this article.

ISEAS Perspective 2022/36, 12 April 2022

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Bilateral relations between Cambodia and Vietnam can be considered a love-hate relationship. As immediate neighbours with a long history of engagement, collaboration and hostility, the two countries have been both friends and enemies. Following the fall of the Khmer Empire in the 15th century, weakened Cambodia was constantly threatened by its two more powerful neighbours, Thailand and Vietnam. To counter the threat from Thailand, Cambodia would establish an alliance with Vietnam and vice versa. Cambodia’s formal relationship with Vietnam began in the early 1600s when Cambodian King Chey Chetha II married a daughter of Vietnamese Lord Nguyen Hy Tong.[1] Through the alliance, Vietnamese migrants were permitted to settle in Khmer territory. The complex relationship between the two countries and between Cambodia and Thailand have also led to Cambodia’s diminishing independence over the past centuries.

The Kingdom of Cambodia, which gained independence from France in 1953, officially established diplomatic ties with the Democratic Republic of Vietnam on 24 June 1967. The relationship was, however, beset with many challenges, both domestic and geopolitical. Despite the ups and downs in their relationship, particularly during the 1970s and 1980s, Cambodia and Vietnam have managed to maintain amicable relations over the past four decades. Notably, both countries have often used such terms as “good neighbourliness, traditional friendship, comprehensive cooperation, and long-lasting stability” to describe their contemporary ties.[2]

During a state visit by Vietnamese President Nguyen Xuan Phuc to Cambodia in late December 2021, Cambodia and Vietnam signed seven agreements covering key areas of bilateral cooperation such as security, defence, education, trade, border, and justice.[3] To mark the 55th anniversary of their diplomatic relations (1967-2022), both countries have agreed to “promote high level contacts and delegation exchanges at all levels, [and] encourage people-to-people exchanges, especially between bordering provinces.”[4] They also emphasized the importance of educating the youth of both countries about their “time-honored friendship, solidarity and mutual trust.”[5]

Notwithstanding their strong and deepening ties,[6] some unresolved issues remain. This article discusses three of these, namely the unfinished border demarcation process, ethnic Vietnamese immigrants, and conflicting views on Vietnam’s role in Cambodia. The article will then outline the way forward to ensure stable bilateral relations.


Unfinished Border Demarcation

One of the key issues between the two countries is the ongoing border dispute caused by the unfinished demarcation of their land border. Thus far, only 84 per cent of the border (1,270 km in length) has been officially demarcated.[7] The undemarcated border areas remain a bone of contention. For example, in April 2020, a total of 31 military tents or shelters set up by Vietnamese authorities, were discovered in an undemarcated area along the border, prompting the Cambodian embassy in Hanoi to demand that the Vietnamese side take them down.[8] Vietnam explained that the shelters were built for its forces to guard the area against illegal immigrants that could potentially spread COVID-19.[9] After some diplomatic exchanges, Vietnam agreed to remove the tents once the pandemic was over.

The border issue with Vietnam remains a hot and sensitive topic in Cambodia. In July 2020, Cambodian Confederation of Unions leader Rong Chhun was arrested after he alleged that there were irregularities in the demarcation process and that some Cambodian villagers had lost their land as a result. He was sentenced to two years in prison for incitement to cause serious disorder to social security.[10] Around 20 young activists were also arrested for protesting for his release. Sam Rainsy, a former leader of the now-dissolved opposition party, the Cambodia National Rescue Party (CNRP), has been at the forefront of the border issue, constantly accusing the Cambodian government, especially Prime Minister Hun Sen, of ceding Cambodian land to Vietnam and allowing Vietnamese immigrants to live illegally in Cambodia. He has long exploited the Cambodia-Vietnam border issue and anti-Vietnamese sentiments to achieve political gains. Now living in exile in France, he has been sentenced many times in absentia on defamation and incitement charges, some of which were related to the sensitive border issue.

At present, many Cambodians share a belief that Vietnam harbours expansionist intentions and wants to encroach on Cambodia’s land whenever possible, despite the fact that anti-Vietnamese sentiments in Cambodia appear to have declined in recent years.[11] Believing that Cambodia had lost Kampuchea Krom (Lower Cambodia) and the island of Koh Tral (Phu Quoc in Vietnamese) to Vietnam in the past, these people are concerned that more land may be lost to their eastern neighbour. Such a belief remains prevalent in certain segments of the Cambodian population, preventing advancement towards sustainable and truly amicable ties between the two countries, particularly at the people-to-people level. It also continues to affect the legitimacy of the Cambodian government, which has been repeatedly accused of operating under Vietnam’s influence.[12]

Ethnic Vietnamese Immigrants

Another issue that affects Cambodia-Vietnam relations concerns unregistered or illegal Vietnamese immigrants in Cambodia. According to the National Institute of Statistics of Cambodia, ethnic Vietnamese made up 0.3 per cent (about 45,500 people) of the Cambodian population of 15.1 million in 2014. Meanwhile, a 2019-2020 national survey shows that there were 27,477 ethnic Vietnamese (or 0.2 per cent of the Cambodian population) in Cambodia.[13] However, estimates on the number of ethnic Vietnamese in Cambodia do differ. For example, one source claims the number to be between 400,000 and 700,000, around 90 per cent of whom have no birth certificates or identity cards.[14] Another reported that in 2019, Cambodia had a total of 80,000 immigrants, 72,000 (about 90 per cent) of whom were Vietnamese.[15] These conflicting figures suggest the complexity of the Vietnamese immigrant issue in Cambodia.

Due to the Cambodian government’s seemingly laissez-faire approach toward Vietnamese immigrants in Cambodia, the issue remains a sensitive topic that continues to influence Cambodian politics and cause division among Cambodian people. It has long been a sticking point between the two neighbours,[16] which can be exploited to fuel nationalist fervour and anti-Vietnamese sentiments among Cambodians, particularly during election campaigns.

In 2019, Cambodian authorities relocated 4,563 families (54 per cent or 2,480 families were of Vietnamese origin) living in floating houses on the Tonle Sap River in Kampong Chhnang Province to live in a designated 40-hectare land area. This move drew much criticism that Cambodia was giving away land to the Vietnamese,[17] reinforcing the suspicion that the Cambodian government is a “Vietnamese puppet.” There has been a long-held conspiracy theory that the current Cambodian government might not be able to operate independently of Vietnamese influence because it was installed by Vietnam in the 1980s.[18] This logic appears to lack concrete supporting evidence, particularly given Cambodia’s closer alignment with China than with Vietnam and its responses to the South China Sea disputes, which show that Cambodia operates independently of Vietnam’s influence and strategic interests.[19] However, the Cambodian government’s current approach (i.e. lack of strong measures in dealing with unregistered Vietnamese immigrants) fails to dispel doubts and criticism about its close ties with Vietnam.

Conflicting Views on Vietnam’s Role in Cambodia

Cambodia went through one of the darkest periods in its modern history in the 1970s when the genocidal Khmer Rouge regime (1975-1979) killed almost two million Cambodians, or around 20 per cent of the Cambodian population at the time. Thanks to the help of Vietnamese forces, the brutal Khmer Rouge regime was ousted on 7 January 1979. However, after the collapse of the Khmer Rouge, Vietnamese troops continued to stay on in Cambodia for ten more years, until 1989.

The date 7 January marks the collapse of the Khmer Rouge regime, and has been celebrated as “Liberation Day” or “Victory Day” by the Cambodian government led by the ruling Cambodian People’s Party (CPP). The celebration pays homage to Vietnam’s critical role in liberating Cambodia from the genocidal regime. However, the same date has also been viewed entirely differently by opposition parties and government detractors. To them, 7 January should be remembered as the day that Vietnam invaded and occupied Cambodia for ten years. These conflicting interpretations have created “division rather than unity, hostility rather than harmony, and tensions rather than cooperation among Cambodians.”[20]

Perhaps cognizant of the controversies surrounding the meanings of 7 January, the CPP has changed how the historic date is celebrated. In the past two years, fewer activities were held and less energy put into the celebration. The COVID-19 pandemic has been cited as the reason for the change. However, some analysts argued that the key reasons were more of a political and strategic nature.[21]

It should be noted that the importance of 7 January in the CPP’s political discourse is also declining as Hun Sen, who came to power during the 1980s with the support of Vietnam, has announced his intention to step down after the 2023 elections. The CPP has endorsed Lieutenant General Hun Manet, Hun Sen’s oldest son, as a prime minister candidate. To prepare Hun Manet for his political campaigns, the CPP needs to adopt a political strategy and a rhetoric that fit his background and achievements, and these have nothing to do with his father’s legacy involving 7 January. Thus, the CPP is aiming to move away from the controversial and divisive 7 January narrative that it has used for decades.

The new strategy can also be seen as part of Cambodia’s bid to distance itself from Vietnam. As mentioned above, 7 January serves as a reminder of both Vietnam’s help to liberate Cambodia from the Khmer Rouge regime and its decade-long occupation of Cambodia in the 1980s. Thus, the CPP may want to move beyond this controversial date to prepare for future elections while limiting Vietnam’s influence and the conspiracy theory surrounding it. All of these take place against the backdrop of the CPP receiving strong backing from China while facing no credible challengers in the coming elections.


To overcome the above challenges, the two countries should consider measures to expedite the border demarcation process. At the same time, the Cambodian government should also find ways to properly address the issue of Vietnamese immigrants and reconcile conflicting views among the Cambodian public about historical issues related to Vietnam.

Expedite the Border Demarcation Process

While working on technical and legal documents,[22] it is essential that both sides expedite the border demarcation process and complete the planting of border markers as soon as possible. This can help mitigate doubts and concerns among Cambodian people about Vietnam’s expansionist intentions. Due to historical reasons, many Cambodians still believe that Vietnam always tries to encroach on Cambodian land whenever feasible. Anti-Vietnamese sentiments remain high, particularly whenever news about border issues with Vietnam arises. Moreover, due to the unfinished border demarcation process and other issues such as Vietnamese immigrants in Cambodia, Vietnam has been “the convenient target for the opposition parties to attack the ruling party so as to consolidate their political positions among voters.”[23] As long as these issues remain, opposition parties in Cambodia will continue to play “the Vietnam card” to achieve political gains, reinforcing anti-Vietnamese sentiments and affecting bilateral ties, especially people-to-people exchanges.

Address the Vietnamese Immigrant Issue

The issue concerning Vietnamese immigrants in Cambodia is complex because many of them have been living in the Kingdom for decades. Their children were born in Cambodia and live their lives as Cambodians. However, they are still considered Vietnamese as their parents are Vietnamese immigrants, some of whom have not obtained legal rights to remain in Cambodia.

It is essential that the Cambodian government find innovative and inclusive ways to solve this long-standing problem. The government needs to establish specific requirements or criteria to grant citizenship or permanent residence to Vietnamese people who have lived in Cambodia for many years. Vietnamese immigrants who cannot fulfil the requirements have to face deportation. This is a controversial approach, yet it needs to be done to pave the way for a sustainable relationship between the two neighbours.

The success of this process requires political will from both governments, particularly the Cambodian side. The goal is to ensure that Vietnamese people who have resided in Cambodia for many years, albeit without legal rights, can lead their lives on equal terms as Cambodians, provided that they meet a set of criteria designed for this purpose. A clear and transparent immigration policy on Vietnamese immigrants needs to be established. The development of such a policy also needs to consider inputs from stakeholders from both countries, including “government officials, historians, researchers, academics, teachers, students, youth representatives and other concerned individuals or groups in the public, private and non-governmental sectors.”[24]

Reconcile the Conflicting Views on Vietnam

Although Vietnam helped liberate Cambodia from the Khmer Rouge regime, it occupied Cambodia for a decade, which have led many Western scholars to consider the intervention an “invasion.”[25] This historical fact should not be denied, distorted, or politicised and be allowed to breed a culture of division, animosity and prejudice between Cambodians and Vietnamese.

In the same vein, the competing interpretations of 7 January—“Liberation Day” versus “Invasion Day”—have created two dominant political narratives in Cambodia, which are harmful to not only Cambodian politics and society but also to Cambodia-Vietnam ties. It is vital to reconcile the conflicting views regarding the meanings of 7 January and the legacy of Vietnam’s removal of the Khmer Rouge. Leaders and politicians of both countries should “leave the debate on the meanings of this historic event to historians who are capable of grounding their argument in sources and critiques rather than specific political agendas.”[26]

It is also crucial for leaders and supporters of both the ruling and opposition parties, particularly the now-dissolved CNRP, to accept 7 January as “both the historic day that Vietnam liberated Cambodia from the Khmer Rouge and the day that Vietnam placed Cambodia under a decade-long occupation.”[27] Promoting one narrative over the other is not helpful because it perpetuates social and political division in Cambodia and encourages anti-Vietnamese sentiments among the Cambodian people.


Given the current context of Cambodian politics, which is shaped by both internal and external factors, such as national interests, nationalist sentiments, electoral politics, and the intensifying US-China strategic rivalry, it can be challenging for Cambodia to maintain good relations with Vietnam due to their long history of animosity and distrust. Although the challenges to bilateral ties identified in this article seem to be under control as both governments are generally on friendly terms, there is no guarantee that this will remain the case in the future. Both countries, especially Cambodia, should therefore find ways to address these challenges.

With Hun Manet being endorsed by his father as the prime minister candidate from the CPP, the prospects of the Cambodia-Vietnam relationship remain uncertain. If Hun Manet is to become prime minister and follows in his father’s footsteps to consolidate power and maintain stability in Cambodia’s ties with its neighbours, Cambodia and Vietnam are likely to remain on good terms. However, in the improbable event that he introduces political reforms and embraces liberal democracy, Cambodia-Vietnam relations will take a new direction, with issues in bilateral ties risking being politicised for electoral gains.

As China’s influence in Cambodia and the broader region grows, the Kingdom is in a delicate situation. It needs to carefully manage relations with Vietnam to avoid antagonizing China, its largest aid provider, foreign investor, and trading partner.[28] However, Cambodia also needs to maintain good and stable relations with Vietnam due to the latter’s proximity and economic, political as well as security significance to the country.


[1] Thearith Leng, “Small State Diplomacy: Cambodia’s Foreign Policy Towards Vietnam,” The Pacific Review 30, no. 3 (2017): 328-347.

[2] Ministry of Foreign Affairs and International Cooperation, “Joint Statement between the Kingdom of Cambodia and the Socialist Republic of Viet Nam on the Occasion of the State Visit of H.E. Nguyen Xuan Phuc, President of the Socialist Republic of Viet Nam, to the Kingdom of Cambodia from 21 to 22 December 2021,” 22 December 2021, https://www.mfaic.gov.kh/posts/2021-12-22-Press-Release-Joint-Statement-between-the-Kingdom-of-Cambodia-and-the-Socialist-Republic-of-Viet-Nam-on-the-occasi-13-33-27

[3] Suos Yara, “A New Chapter in Cambodia-Vietnam Bilateral Ties,” Phnom Penh Post, 22 December 2021, https://www.phnompenhpost.com/opinion/new-chapter-cambodia-vietnam-bilateral-ties.

[4] Ministry of Foreign Affairs and International Cooperation, “Joint Statement.”

[5] Ibid.

[6] See Suyheang Kry and Terith Chy, “Cambodia’s Relations with Vietnam: Prospects and Challenges,” in Cambodia’s Foreign Relations in Regional and Global Contexts, edited by Sok Udom Deth, Suon Sun and Serkan Bulut (Phnom Penh: Konrad-Adenauer-Stiftung, 2018): 63-82.

[7] Phnom Penh Post, “Border Demarcation Effort Sped Up,” 24 October 2021, https://www.phnompenhpost.com/national/border-demarcation-effort-sped.

[8] Joshua Lipes, “Vietnamese Military Shelters Remain in Disputed Border Area Despite Cambodian Diplomatic Protest,” Radio Free Asia, 22 May 2020, https://www.rfa.org/english/news/cambodia/shelters-05222020154046.html.

[9] Ibid.

[10] Kim Sarom, “Chhun Sentenced to Two Years,” Phnom Penh Post, 18 August 2021, https://www.phnompenhpost.com/national/chhun-sentenced-two-years

[11] Alastair McCready, “Is Anti-Vietnamese Sentiment on the Decline in Cambodia?,” Southeast Asia Globe, 7 January 2021, https://southeastasiaglobe.com/cambodia-vietnam-relations/.

[12] Kry and Chy, “Cambodia’s Relations with Vietnam.”

[13] National Institute of Statistics, “Report of Cambodia Socio-Economic Survey 2019/20,” 2020, https://www.nis.gov.kh/index.php/en/14-cses/86-cambodia-socia-ecomonic-survey-2019-20.

[14] Minority Rights Group International, “Cambodia – Ethnic Vietnamese,” 7 November 2017, https://minorityrights.org/minorities/ethnic-vietnamese/.

[15] Khorn Savi, “Kingdom Rejects VN Request,” Phnom Penh Post, 20 August 2019, https://www.phnompenhpost.com/national-politics/kingdom-rejects-vn-request.

[16] Ibid.

[17] Phoung Vantha, “Cambodia Says Relocated Vietnamese Families Cannot Own Land,” Cambodianess, 12 December 2019, https://cambodianess.com/article/cambodia-says-relocated-vietnamese-families-cannot-own-land.

[18] John D. Ciorciari & Jessica Chen Weiss, “Nationalist Protests, Government Responses, and the Risk of Escalation in Interstate Disputes,” Security Studies 25, no. 3 (2016): 546-583.

[19] Veasna Var, “Cambodia’s South China Sea Policy: From ASEAN Aligned to Echoing Chinese Clientism,” in Security, Strategy, and Military Dynamics in the South China Sea: Cross-National Perspectives, edited by Gordon Houlden, Scott N. Romaniuk and Nong Hong (Bristol: Bristol University Press, 2021): 193-214.

[20] Heng Kimkong, “January 7 in Cambodia: One Date, Two Narratives,” The Diplomat, 16 January 2019, https://thediplomat.com/2019/01/january-7-in-cambodia-one-date-two-narratives/.

[21] Ben Sokhean, “CPP Slams Slander over Victory Day Celebration,” Khmer Times, 10 January 2022, https://www.khmertimeskh.com/501003718/cpp-slams-slander-over-victory-day-celebration/

[22] Suos Yamy, “Demarcation ‘Complicated,’” Phnom Penh Post, 24 June 2020, https://www.phnompenhpost.com/national/demarcation-complicated

[23] Nguyen Vu Tung, “Vietnam-Cambodia Relations: An Analysis from a Vietnamese Perspective”, in Cambodia’s Foreign Relations in Regional and Global Contexts, edited by Sok Udom Deth, Suon Sun and Serkan Bulut (Phnom Penh: Konrad-Adenauer-Stiftung, 2018): 83-100.

[24] Him Raksmey and Heng Kimkong, “Taking Cambodia-Vietnam Relations to New Heights,” Cambodian Institute for Cooperation and Peace, 13 July 2020, https://cicp.org.kh/wp-content/uploads/2021/02/CICP_Op_Ed_Series_Him_Raksmey_and_Heng_Kimkong_Taking_Cambodia_Vietnam_Relations_to_New_Heights.pdf

[25] Theara Thun, “‘Invasion’ or ‘Liberation’?: Contested Commemoration in Cambodia and Within ASEAN”, TRaNS: Trans-Regional and-National Studies of Southeast Asia (2021): 1-17, https://doi.org/10.1017/trn.2020.17.

[26] Ibid.

[27] Heng, “January 7 in Cambodia.”

[28] Po and Primiano, “An ‘ironclad friend.’”

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