In a decision that unblocks months of delays and protracted negotiations, the government of Thailand has officially approved the modification of the contract for the purchase of new S26T attack submarines from China for a value of USD 370 million, after authorizing the replacement of the German-made MTU-396 diesel engines with the CGD620 models manufactured in China. This resolution, which also extends the construction timeline of the units to 1,217 days, allows progress on a program aimed at strengthening the operational capabilities of the Royal Thai Navy, ensuring national security, and protecting the country’s maritime interests.
A program with years of ups and downs
By way of recap, Thailand had selected Chinese Yuan-class submarines in 2015, in their export version (derived from the Type 039A), for their favorable cost-benefit ratio compared to other offers. At that time, the navy had no submarines in service since the retirement of the veteran Matchanu class, so the contract signed in 2017 with the China State Shipbuilding Corporation (CSOC) for USD 403 million represented a key qualitative leap.
The project encountered its first major obstacle in 2021, when Germany blocked the export of the MTU-396 diesel engines that are part of the Chinese submarines offered. This refusal, based on political restrictions on the transfer of military technology to China, prevented Beijing from delivering the agreed propulsion systems. In this scenario, Prime Minister Prayut Chan-o-cha warned at the time that the contract would be canceled if the initial specifications were not respected. As a result, China offered its CHD620 engines as an alternative, produced locally and certified by MTU, but the proposal was rejected and the program was left in limbo.
Alternative options and pause in the acquisition
During the suspension of negotiations, the Thai Ministry of Defense evaluated options to compensate for the absence of an operational submarine, considering the acquisition of an anti-submarine frigate or an offshore patrol vessel. Finally, the head of the Defense portfolio, Sutin Klungsang, announced the selection of a frigate, although the operation never materialized. This indecision generated criticism both in the political arena and in local media.
Resuming the path toward the S26T
As months went by, 2024 brought new developments. In May, following a visit by representatives of the Chinese naval industry and the PLA Navy, Bangkok once again expressed interest in resuming the purchase of S26T submarines, putting the option of domestically manufactured CHD620 engines back on the negotiating table. There was even speculation about expanding the order to two units, although that intention did not materialize.
The final approval and progress in construction
Now, in 2025, the Thai government has formally approved the change of engines, allowing the program to resume and extending the delivery deadline. According to local media, the physical progress of the project already reaches 64%, with 10 of the 18 scheduled payments completed, equivalent to 7.7 billion baht. The outstanding balance amounts to 40% of the contract, about 5.5 billion baht. The confirmation not only ensures that Thailand will finally incorporate an S26T attack submarine into its fleet but also represents an endorsement of naval cooperation with China in a regional context marked by the accelerated modernization of Southeast Asian navies.
Images used for illustration purposes only.
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