I agree with Ysabella on the sugar in Thai food, especially the curries. Larb (chopped or ground meat seasoned with lime, fish sauce, basil, mint, cilantro) is a pretty safe bet, though it's a bit low in fat for my taste. It can be found in the salad section of the menu.

I recently went to Angel's Thai on 4th in Olympia - the chef was willing to leave the sugar out of the Tom Yum for us and it was excellent.