2024/22 “Thailand’s Submarine Saga Reaches a Climax in March” by Paul Chambers and Termsak Chalermpalanupap

Thailand’s Navy has been struggling to obtain three advanced submarines from China since 2015. Picture of a Yuan-class Chinese submarine taken from the Facebook Page of the U.S. Naval Institute. Accessed 20 March 2024.


  • Since 2017, Thailand’s Navy has been struggling to obtain three advanced submarines from China.
  • Reasons for buying the Chinese submarines included keeping up with neighbours (amidst a regional arms race), attaining an “awe factor,” appeasing China, and improving naval capacities.
  • The submarine purchase was hindered by parliamentary opposition pointing to their impracticality in shallow waters, high financial costs amidst other priorities such as the 2020 advent of the COVID-19 pandemic, and Germany’s refusal to allow export of Germany-made submarine engines to China.
  • In 2021, the Thai government of General Prayut Chan-o-cha delayed paying instalments for the first submarine while the engine issue remained unresolved. Funding for the purchase of the second and third Chinese submarines has also been suspended.
  • Now, the Srettha Administration is exploring all practical options, and a potential positive breakthrough in March is in the offing.

* Paul Chambers is Lecturer and Special Advisor for International Affairs, Center of ASEAN

Community Studies, Naresuan University, Thailand. In March-May 2021 and January-June 2024, he was Visiting Fellow in the Thailand Studies Programme at ISEAS – Yusof Ishak Institute. Termsak Chalermpalanupap is Visiting Fellow and Coordinator of the Thailand Studies Programme, ISEAS – Yusof Ishak Institute.

ISEAS Perspective 2024/22, 22 March 2024

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The ongoing saga of the Royal Thai Navy (RTN) to buy three Chinese submarines is heading towards yet another intriguing climax. Defence Minister Sutin Klungsang plans to seek a Cabinet decision in March on how the RTN shall proceed.

Most probably, the Cabinet will be asked to endorse the RTN’s proposed acceptance of four China-made diesel generator engines (the number typical in fleet-type subs)[1] – instead of better German-made ones, which are now unavailable – to fit into the first S-26T submarine[2] which the RTN has ordered from China Shipbuilding & Offshore International Company (CSOC) since May 2017.

However, it remains unclear whether Minister Sutin will support the RTN’s original plan of buying up to three Chinese submarines, altogether costing about 36 billion baht (US$996 million). 

Since the pandemic has ended and the Thai economy has regained steady growth, the RTN apparently feels that it is now appropriate to ask once again for the money to pay for two more Chinese submarines. After all, the Royal Thai Air Force (RTAF) is also going to ask for an urgent allocation to buy a squadron of new F-16 (Block 70th) fighters, costing about US$63 million each.


In the 1932 Revolution which ended the Siamese absolute monarchy, the naval faction in Kanarasadorn (People’s Party) was an active and influential third party in the power struggle between the army and the civilian faction. 

By the early 1930s, Thailand’s Royal Thai Army (RTA) and the RTN were increasingly large forces financially competing for procurement from abroad. In 1938, the RTN purchased and received from its Axis Power ally (Imperial Japan) four Mitsubishi-constructed submarines at a cost of 3.28 million baht (about US$97,312). The deal included submarine training for the Thai crew.[3] This made the RTN the first navy in Southeast Asia to have submarines. Thailand also bought from Japan two light gunboats,[4] and, from its Axis ally Italy, two light cruisers. 

The RTN received the first of four Japan-built submarines on 25 May 1938. The RTN has thus celebrated 25 May as “Submarine Day”. All four small coastal submarines arrived in Thailand on 29 June 1938. They took part in fighting the French navy in January 1941 around Koh Chang near the Thai-Cambodian maritime boundary.[5]

After World War II, the four Thai submarines were in a bad state of disrepair, and were eventually decommissioned on 30 November 1951. 

In 1946, the RTN’s military procurement patron became the United States. Washington sold or provided coastal patrol boats, minesweepers, a frigate, and a dredger, with the final delivery arriving in 1954.

 In a June 1951 ceremony marking the US handover of dredger SS Manhattan to the RTN, Prime Minister Field Marshal Phibun Songkram, who had come aboard Manhattan to officially take charge of it, was detained at gunpoint by naval officers attempting a coup. The influential army field marshal was placed onboard the RTN’s flagship HTMS Sri Ayutthaya. But the RTA, the RTAF, and the Royal Thai Police (RTP) refused to support the navy’s coup attempt. Warplanes bombed navy facilities and eventually sank Sri Ayutthaya. PM Phibun managed to escape unharmed and quickly rallied his forces to crush the rebellion.

In the ensuing crackdown, more than 70 senior naval officers implicated in the rebellion were arrested, expelled from the RTN, and jailed. They included the submarine force commander, Rear Admiral Kanok Noppakhun. 

After the failed coup, the RTN’s budget was heavily axed, and much of its hardware was given to the RTA or the RTAF. In addition, military procurement for the RTN was cut to a minimum (only three small landing ships were obtained by the RTN from 1962-1973).[6] 

In the 6 October coup of 1976, RTN Commander Admiral Sa-ngad Chaloryu was nominally appointed the coup leader, because of his military seniority as he was then concurrently the Supreme Commander. The actual coup was plotted mostly by senior army generals without much involvement of the RTN. The admiral was similarly appointed leader of the October 1977 coup which overthrew the right-wing royalist government of Thanin Kraivichien.

In 1978, with the accession of arch-royalist General Prem Tinsulanonda as Army commander, the RTN again diminished in influence. General Prem went on to become Prime Minister (1980-1988). Once again, the RTA and the RTAF received procurement priority over the RTN. The RTAF, in particular, was favoured because Crown Prince Vajiralongkorn developed a keen interest in flying F-5 jet fighters.


When the Cold War ended in 1992, the RTN tried to obtain funding for submarines and other military hardware from almost every successive government. The newly elected civilian government of Chuan Leekpai (1992-1995) did not veto the RTN’s purchase from Spain of the first aircraft carrier in Southeast Asia (a helicopter carrier called the HTMS Chakri Naruebet). It began service in 1997, the very year of the Asian Financial Crisis.[7]

The RTN seemed on its way to finally gain a sufficient budget for the modern procurement of equipment  to become a competitive navy. But the economic crisis diminished funding for operating the carrier such that only a limited use was possible.[8] Even up to 2024, it has remained an effective “white elephant”, carrying no aircraft. Meanwhile, the RTN has acquired smaller vessels, with China, the United States, and South Korea as its principal sources of hardware.

Though Chuan had vetoed RTN efforts to acquire submarines in 1994, the RTN re-introduced the proposal to Chuan’s successor, Prime Minister Banharn Silapa-archa (1995-1996), in 1995.

But allegations that the chosen submarine manufacturer, Swedish Kockums, had bribed Banharn’s political party to accept the deal, caused a firestorm in Thailand. Thereupon, parliament voted against the submarine purchase.[9] And when the idea of submarines was brought before Banharn’s successor Prime Minister General Chavalit Yongchaiyudh (1996-1997), the Asian financial crisis had hit, and prevented any such purchase. 

Under the 2001-2006 Thaksin government, Defence Minister General Chavalit blocked the RTN from purchasing submarines because of the high price-tag. However, there were reports that China was on the verge of selling diesel-electric Romeo-class submarines to the RTN. The 2006 RTA-led coup against Thaksin Shinawatra ended any such transaction.[10]

After the coup-borne 2006-2008 regime of General Surayud Chulanond, the RTA and the RTAF subsequently gained military hardware. Not the RTN.[11] In 2007, King Bhumibol apparently showed his disapproval of the RTN’s idea of acquiring submarines, joking that they would probably get stuck in the mud in the shallow Gulf of Thailand.[12]

During the Abhisit administration (2008-2011), China offered to sell two Song-class submarines to Thailand, which were in need of extensive modernisation.[13] Then, there was a move to purchase two more capable though pricier U209 submarines from South Korea.[14] But the RTN, which preferred Western technology, opted instead to buy two to six second-hand diesel-electric German U206A submarines. However, a 2011 change in government ended the RTN’s submarine purchase attempt.[15]

The Yingluck government (2011-2014) rejected the U206As in favour of cheaper Chinese or Russian submarines,[16] and by 2012 was furthermore prioritising buying frigates over submarines; the RTN fell in line obediently.[17]

During the past seven decades, the RTN has thus been nurturing a dream of reviving its submarine force. One big justification was and still is the need to have Thai submarines as deterrent against neighbours whose navies have deployed submarines.[18] 

The RTN saw a new opportunity to resurface its submarine programme after the May 2014 coup which toppled the Pheu Thai-led government of Prime Minister Yingluck Shinawatra. The military regime led by coup leader General Prayut brought new hope to the RTN.

The RTN sent teams to look for the best possible submarine options. In early July 2015, RTN Commander Admiral Kraison Chansuwanit disclosed the RTN’s choice of three Chinese submarines, based chiefly on recommendations from RTN’s submarine officers.

The commander mentioned that submarine producers from six countries, including China, Germany, Sweden, and South Korea, had been approached. And CSOC offered the best deal with a proposal to sell three Yuan-class submarines, equipped with Germany-made MTU diesel-electric engines and the air-independent propulsion (AIP) system which will enable the submarines to stay submerged for up to 21 days without resurfacing for air. A non-AIP submarine can stay submerged for up to only five days. 

In March 2017, Prime Minister General Prayut voiced support for the RTN’s programme to buy the three Chinese submarines, which he described as “Buy 2 Get 1 Free”. The programme involved spending about 36 billion baht for three Chinese submarines of the Yuan-class. The RTN would designate the China-built submarines as the S26T class, which General Prayut said would be “the cheapest, and good enough”.[19] 

On 18 April 2017, the Cabinet approved the allocation of 13.5 billion baht for the purchase of the first S26T submarine from CSOC. 

On 1 May 2017, RTN Chief of Staff Admiral Luechai Ruddit led a team of naval senior officers to explain officially for the first time in a press conference the RTN’s submarine programme. Admiral Luechai outlined five major reasons for buying the Chinese submarines.[20]

Another likely reason to buy the Chinese submarines, despite the RTN favouring those from Europe, was to send a signal to the United States. Thailand has been since 2003 a “non-NATO ally” of the United States. But Washington had criticised Thailand’s military for carrying out the May 2014 coup against an elected government—what Greg Raymond calls “dominance denial messaging.”[21]

In addition, the RTN’s interest in buying Chinese submarines reflected the growing amity between the two geographically-close countries. China has been for several years the top trading partner for Thailand, as well as the largest source of foreign tourists to Thailand.


After the 2019 general election, General Prayut returned as prime minister as well as concurrently defence minister of a new coalition government led by the pro-military Palang Pracharat Party. His support for the RTN’s submarine programme continued.

But by April 2020, parliamentary opposition to the RTN’s submarine programme amidst growing economic malaise, fears that generals only wanted submarine-related kickbacks, and the onset of the COVID-19 pandemic, forced the Prayut government to delay funding the submarine purchase. Budget allocation for the second and the third submarines were put on hold until after COVID.[22]

In February 2022, new formidable issues seemed to be dooming the submarine programme. First it was discovered that CSOC was unable to buy German MTU396 diesel engines, because Germany by law could not allow export of these engines to China (given the embargo of the EU and Germany on military hardware for China) to be fitted on submarines to be sold to the RTN.

A second problem was that it was discovered that the submarine deal might not be a formal government-to-government deal. Indeed, allegations grew that CSOC, a state enterprise in charge of building the S26T, and accompanying submarine dock/facilities, had listed its naval engineers coming to Thailand as international school-teachers instead of employees of CSOC. CSOC’s own representative in Thailand was listed as a Thai business, Natthaphon Co., Ltd., which had donated US$56,599 to Deputy Prime Minister General Prawit Wongsuwan’s Palang Pracharat Party.[23]

While the second problem faded, the export ban of German engines did not. CSOC offered in place of the German engines, Chinese-made CHD 620 engines, which incidentally had never been used in submarines. But by August 2022, RTN Commander Admiral Somprasong Nilsamai had refused to change the original submarine agreement which required the use of the German engines. If China could not deliver the first submarine with German engines before 2024, then the agreement would be null and void.[24]

Admiral Somprasong’s successor Commander Admiral Choengchai Chomchoengpaet, was more flexible towards the Chinese. Under him, CSOC and the RTN worked out an agreement whereby the Chinese would have to provide appropriate compensation regarding breach of the agreement about the S-26T submarine engines; and during the period before the S-26T delivery, China would have to temporarily provide one or two used Type 039A submarines for the RTN to train on.


Being the chief opposition party during the Prayut Administration (2019 – 2023), Pheu Thai (PT) used to vigorously oppose the RTN’s submarine programme. The most outspoken critic was MP Yutthapong Charas-sathien, a deputy PT leader from the northeastern province of Mahasarakam. Yutthapong questioned the validity of the so-called “Government–to– Government” agreement between Thailand and China on the purchase of the three Chinese submarines. 

He contended in a dramatic press conference on 23 August 2020 that the admiral representing the Thai Government to sign the agreement in Beijing on 5 May 2017 lacked “full powers”; and the “secret” agreement, which he showed during the press conference, did not bind the RTN to buy up to three Chinese submarines.[25] Yutthapong is now an advisor to Prime Minister Srettha Thavisin.

At the same time, Sutin Klangsang, also a deputy PT leader and a veteran politician from Mahasarakam, was the opposition chief whip. He had on numerous occasions criticised the RTN for its alleged lack of transparency and unwillingness to share pertinent information with the House of Representatives. He and the PT accused General Prayut of trying to appease the RTN in pushing for the three Chinese submarines, in total disregard of the plight of the poor Thais suffering in economic hardship during the COVID-19 pandemic. 

Now, with the PT becoming the chief government party, and Sutin being the new defence minister, the PT and Sutin are facing a sticky dilemma on what to do with the RTN’s troubled submarine programme.

Sutin has the distinction of being the first civilian politician to hold the defence minister post without concurrently holding the premiership. The highly influential but sensitive defence portfolio is traditionally held concurrently by a prime minister,[26] or by an ex-military man. 


During his introductory visit to the RTN Headquarters last October, Defence Minister Sutin acknowledged that there had been pending issues in the submarine programme, and he would try to find a pragmatic solution that would be in the Thai national interest, and that would uphold the good relations between Thailand and China. He interestingly mentioned one  new idea: Instead of getting the S26T submarine, the down payment of about 6 billion baht paid to CSOC could go to paying for a Chinese frigate, or a smaller offshore patrol vessel (OPV).[27] The latter would replace the sunken “Sukhothai” corvette.[28]

Just to play safe, in November 2023, Navy Commander Admiral Adoong Pan-iam sought legal advice from the Office of the Attorney-General on three particular points: Whether replacing the German engines with the Chinese engines would constitute a “substantive change” in the agreement on the S26T submarine? If it did, then how and who can authorise such a “substantive change”? And whether or not exchanging the submarine to a frigate will also constitute a “substantive change”?[29]

Subsequently, in early February, Minister Sutin disclosed that the Attorney-General Office’s response was quite positive and clear: the Cabinet has the authority to authorise the RTN to negotiate on any “substantive change” in the submarine agreement.[30]


Minister Sutin set up an ad hoc advisory committee to examine all pros and cons of every proposed solution, and this was headed by General Somsak Roongsita, an advisor to the defence minister.

The committee met twice in February and will soon submit its findings and recommendations to Minister Sutin. After that, Sutin plans to present the RTN’s case at a cabinet meeting in March. Most probably, he will want the Cabinet to approve the RTN’s acceptance of the Chinese engines in the first S26T submarine. 

After all, the RTN is apparently determined to proceed with its submarine programme. Construction of a submarine berthing pier and weapon storage facilities in Sattahip naval base has been ongoing. HTMS “Chang”,[ the huge China-built multi-purpose amphibious landing platform ship has been commissioned since last April, and it will soon be refitted to serve as a submarine tender ship.

How far Minister Sutin and the PT are prepared to support the RTN’s submarine programme remains unclear, particularly on the question of getting the second and the third Chinese submarines. 

The Srettha government is financially stretched; it does not have money (about 500 billion baht are needed!) to fund its ambitious “Digital Wallet” programme to give every poor Thai who is 16 years old and above 10,000 baht worth of digital credit to spend, with the aim of stimulating the Thai economy.

The RTN has always maintained that ideally, at least three submarines should be bought to constitute a credible and effective deterrent: one to patrol the Gulf of Thailand, one to operate in the Andaman Sea, and one for training as well as to be on stand-by to replace either the one in the Gulf of Thailand or the one on the Andaman Sea should the need arise. 


The troubled saga of the RTN’s submarine programme will reach a climax in March. It looks very likely that the RTN will get its first China-built submarine equipped with Chinese engines.

This will be good news to the RTN, and will help salvage its lost prestige of being overwhelmed by the RTA and surpassed by the RTAF.

However, the RTN may have to wait a little bit longer to get its second and third China-built submarines. Neither Defence Minister Sutin nor Pheu Thai want to be seen asking for 22.5 billion baht to pay for two more submarines when the country is supposedly facing an impending economic crisis owing to deflation and the loss of general purchasing power in Thailand.


For endnotes, please refer to the original pdf document.

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