I was recently in Mississippi visiting my folks, and we stopped through Hattiesburg, surprisingly stumbling across one of the best Thai restaurants I've ever visited. The chef/owner worked at Essex House in NY for 15 years under Alain Ducasse, and now owns an amazing little spot in bum**** Mississippi.
So why don't we have any good places here in Austin? First of all, I have one fault in my logic... I often judge a Thai place by their Pad Thai, one of the most American-friendly dishes. That said, it's always seemed to be a good barometer. Places like Thai Passion and Madam Mam's present a completely chile-coated, orange glop of a dish; the good stuff should be light brown and not overpowering. You should be able to tasted the tamarind, peanuts, bean sprouts and cilantro. I love hot, but making the dish about heat and only heat is just wrong. Believe it or not, my Pad Thai test usually works though; if the Pad Thai's good at a restaurant, the rest is usually great, too.
The best PT I've had in town has been from Java Noodles (which unfortunately doesn't really offer any other Thai dishes) and Subsin's, a grungy little place on Manchaca that a Thai friend recommended as the best Thai place in town. I'm never really down in that area though, and I'm not even sure if it's still open.
The place in MS had a great dish with shrimp cooked in spicy sambal-ish sauce, garnished with tiny slivers of kaffir lime leaves. It was delicious. In a town where we have almost every other Asian cuisine represented, there HAS to be a good Thai place that I'm overlooking... recommendations, anyone? I'd like to find somewhere that's got some more interesting things than your typical fare, but I'd settle for some good PT, Nuea Pad Prik and Tom Kha.