Unlike with Chinese, it is not impossible to make a Thai scrabble, but I doubt there is one, given the size of its alphabet (http://en.wikipedia.org/wiki/Thai_alphabet)
i've been to the king's cup tournament in bangkok a couple of times. there's a children's tournament run in parallel in the same venue, and it was a truly amazing sight to see thousands of kids squaring off across scrabble boards. i truly wish school scrabble would take off in india; as it is, this year we didn't even manage to find two kids to go for the world youth scrabble championship :(