Defense & Security 2025: China on track with Thai submarine delivery

A model of the S26T diesel-electric submarine that Thailand ordered in 2017 is seen displayed at Defense & Security 2025 in Bangkok. (Janes/Jon Grevatt)

The China State Shipbuilding Corporation (CSSC) has confirmed that it is on track to deliver the Royal Thai Navy's (RTN's) on-order S26T diesel-electric submarine (SSK) within three years.

An official from CSSC told Janes on 10 November at the opening day of the Defense & Security 2025 show in Bangkok that, following years of delays over the choice of the submarine's engine, Thailand's S26T programme is gathering pace with delivery expected by the end of 2028.

“The new engine is fully approved by the Thai side and is being fitted into the new submarine as announced under our recent agreement,” the CSSC official said.

He added that CSSC has held discussions with the RTN about the supply of additional S26T submarines but that a Thai decision on such an order is only likely following the delivery of the initial boat. “I think [the RTN] wants to wait and see the performance of the first submarine,” the CSSC official said.

In September 2025, the RTN and China Shipbuilding & Offshore International Co Ltd (CSOC) – a CSSC subsidiary – signed a revised S26T contract that called for the delivery of the submarine within about 40 months.

The revised agreement also confirmed that the submarine will be powered by China's CHD620 marine diesel engine instead of Germany's MTU 396 powerplant, which was the engine of choice when Thailand signed the original S26T purchase contract in 2017. However, Germany has refused to export the engine to China for fitting onto the RTN's submarine, citing export control restrictions.