[1] He claimed two gold medals in the 50 m freestyle at the Southeast Asian Games (2003 and 2005), before losing out to Daniel Coakley of the Philippines in 2007.

[2][3] Chinnapasaen qualified for the men's 50 m freestyle at the 2004 Summer Olympics in Athens, by posting a FINA B-standard entry time of 23.20 from the Southeast Asian Games in Hanoi, Vietnam.

[2][4] He challenged seven other swimmers on the sixth heat, including three-time Olympian Julio Santos of Ecuador.

Chinnapasaen failed to advance into the semifinals, as he matched a forty-sixth place tie with SEA Games medalist and former rival Allen Ong of Malaysia in the preliminaries.

[5][6] Chinnapasaen is currently Head of Aquatics at St Andrews International School Bangkok.