Many of the nations of Southeast Asia are developing or expanding their submarine fleets. Malaysia, Singapore and Indonesia already possess submarines.
Vietnam has taken possession of the first of six Russian-built Kilo class boats, with Myanmar determined to have a submarine force by 2015. Thailand has naval officers training abroad in Germany and South Korea.
The New York Times sees this expansion as a direct result of recent aggressive Chinese activities in the South China Sea and the Indian Ocean. For more, see the article here.