Northern Illinois University -> SEAsite -> Thai Classical Music
This is a truly excellent explanation of everything in Thai music, from the scale system to the instruments to history to ensemble; there are even interactive lessons and some amusing shockwave games.

http://www.dontrithai.com/media.htm
dontrithai.com is a great website with great mp3s.
 

http://en.wikipedia.org/wiki/Southeast_Asian_music
Wikipedia entry on SEAsian classical music

http://www.medieval.org/music/world/sea.html
Brief tour of SEAsian classical music

peace everyone =)