Thai is tough - everything is drowned in oil. Even the tofu is usually deep fried. I would order a small salad before dinner and just what looks reasonable on the individual menu at the restaurant. There are usually some dishes that aren't too bad. I haven't eaten Thai in awhile because I got spoiled with great Thai restaurants in Seattle.

chicken satay on the appetizer menu paired with a salad dressed in lime juice and a bowl of soup

some places have fresh spring rolls that are not deep fried ~these are really yummy, easy to make at home, and totally lo-cal

ask the waitress about what kind of sauce is on the dishes

most thai dishes have at least some coconut milk in there :/ or better yet, peanuts :( . However, while it is high in fat, coconut milk has a ton of nutrients in it that are good for you. So, if you can find a dish that only has a little coconut milk (or is made with reduced fat coconut milk), then it'll probably be okay for one meal