Depends on the curry, and what they put in it.
Usually, the main ingredients in the sauce are coconut milk and curry paste.

If the coconut milk is unsweetened, and the curry is made with favorable vegetables (e.g. no pineapple or such), it would probably be OK. This is a long shot, though.

Atkins.com has this advice on thai food.

H -- who now needs to go eat Thai.