China will Hand Over the S26T Submarine to Thailand in 2028

02 September 2025

Model of Royal Thai Navy (RTN) S26T Submarine displayed at Royal Thai Fleet (RTF) headquarters gate of Sattahip naval base in Chonburi Province, Thailand (photos: Royal Thai Navy)

One of the key defense projects approved by the Thai Cabinet at its meeting on 5 August 2025, for the Royal Thai Navy, included the approval of a government-to-government (G-to-G) contract amendment for the long-running Chinese S26T submarine program, following the Thai Ministry of Defense's approval of the previous contract amendment in late June 2025.

The essence of the contract amendment is the acceptance of the switch to the CHD620V16H6 generator-driven engines instead of the MTU 16V396SE84-GB31L generator-driven engines for the S26T submarine, following Germany's refusal to export them to China following the tightening of European Union (EU) sanctions, and the German company MTU shutting down its MTU 396 family engine production line in 2020.

As the Royal Thai Navy revealed, the first S26T submarine is 63 percent complete. The contract amendment will allow for the installation of three CHD620V16H6 engines per submarine and extend the delivery period by 1,217 days, approximately three years and four months, or around 2028. However, given the speed at which China has been building the first four Pakistani Hangor-class submarines, with the second and third submarines being launched just 155 days apart (approximately five months), the completion time may be even shorter.

Although the Royal Thai Navy has clarified the necessity and transparency of the project and expressed confidence in proceeding with the first phase of the S26T submarine procurement, it has also been discovered that a model of the S26T submarine, based on the Type 039B submarine in service with the People's Liberation Army Navy, has been installed near the Inshore Patrol Ship (T.99) Memorial in front of the Fleet Operations Command (FOC) at the Sattahip Naval Base in Chonburi Province.

But the issue of the engine driving the generator that has been in place since 2021, which the Thai government officials have just made a decision to amend the contract as advised by the Royal Thai Navy or cancel the project and pay the money that has already been paid, 7,724,140,522 baht ($238,915,622) or 63 percent, leaving 5,540,859,478 baht ($171,384,490) or 37 percent to be paid after a long postponement.

This has caused the delivery of the S26T submarines, Phase 1, as per the contract signed on 5 May 2017, from the original date of 2023, to be delayed by almost two times (11 years). And as it is a political issue both in Parliament and the public sector that opposes the Royal Thai Navy's submarines, the approval of the S26T submarines, Phase 2 and Phase 3, the second and third submarines, totaling three submarines, may be difficult to follow and will affect the first submarine as well.

While waiting for the selection of personnel to be trained in preparation for the delivery of the submarine in China, the Royal Thai Navy continues to conduct submarine training with friendly countries, including sending personnel to participate in the International Diesel Submarine School (IDSS) and the Naval Submarine School (NSS) of the United States Navy at New London Naval Submarine Base in Connecticut.

Four Royal Thai Navy personnel, along with one officer from the Republic of Korea Navy, completed the International Diesel Submarine 2025 course on August 7, 2025. Two Thai naval officers, one with the rank of Lieutenant Commander and one with the rank of Lieutenant Commander, are assigned to the frigate HTMS Chao Phraya, and it is understood that they are or have been in the Anti-Submarine Warfare (ASW) line of duty.

Royal Thai Navy Submariners who recently graduated from the US Naval Submarine School's International Diesel School (photo: Naval Submarine School)

One Lieutenant Commander from the Royal Thai Fleet (RTF) and one Lieutenant Commander wearing Naval Special Operations Field Uniforms and displaying RTN SEAL and RTMC Marine Paratroopers course insignia, reflecting the diversity of units trained to develop the Royal Thai Navy's submarine knowledge.

Frigate procurement project

The Royal Thai Navy has also approved a budget for the fiscal year 2026 for the first phase of the new frigate procurement project, valued at approximately 17.5 billion baht ($533,617,930). This follows the Royal Thai Navy's request for approval of two frigates, valued at 35 billion baht ($1,067,235,860), to be built in Thailand under the 2026-2032 budget commitment, out of a total of four required by 2037.

According to recent reports in Thai media, there are five countries that are expected to be potential competitors: Damen of the Netherlands, which is proposing the SIGMA frigate design, Hanwha Ocean of the Republic of Korea, which is proposing the Frigate 4000 design.

The German company TKMS is working with the Thai company Marsun, which is proposing the MEKO A-100 frigate design, the Spanish company Navantia, which is likely to offer the ALFA 3000 frigate design, and the Italian company Fincantieri, which is likely to offer the FCX30 frigate design. The process is expected  to begin in fiscal year 2026, or from October 1, 2025 onwards.

(AAG)