I have thai language module for xoops2. Not perfectly done.
But you can try. And give me a comment. I use charset=windows-874 for encode. Edit and modify by just
using a notepad. Tricky part is when save notepad have to
choose endcoding as UTF-8. Install by just copy those folder
to corresponding language folder. Then log in as Admin
then choose preference language to "thai"

File is on this link

ftp://ftp.enaca.org/pub/xoops/thai_language_pack.tar