A model of a Chinese S20 (or S-20) submarine at an arms trade show. Note that it is being marketed by "CSOC" - which is the China Shipbuilding & Offshore international Co (CSOC) Ltd.
A Chinese Type 039A or Type 041 Yuan class submarine - with many Russian Kilo characteristics. Thailand has been puzzling whether to buy 3 small version Yuans - called "S-20" or "S-26T".
For the latest on Thailand's on-again, off-again interest in submarines see Submarine Matters Does Thailand Need Submarines At All? August 12, 2015.
Please connect with my Chinese Yuans for Thailand and Pakistan? June 27, 2015. It looks like I was right (in the June 27 article) in being cautious - I said "China is an unconfirmed choice" and "If China is finally chosen".
The whole process of Thailand selecting Chinese submarines looked strange from the beginning. The "process" being a mere Naval Committee deciding on Chinese submarines and then publicising the decision before the Thai Cabinet had signed off on it.
It all looks like a face saving formula where the Thai military government only indirectly proposed submarines. But high defence spending was/is unpopular with sections of the public. Other competing spending priorities, such as reformed healthcare, were raised.
Perhaps only two Chinese submarines, or other subs, might be bought at some point in the future.