If you want thai food as it should be at reasonable prices, go to Suda off Sukhumvit and eat with the locals! Order a few mains along with rice (pronounced "lie") and tuck in - you won't find it better anywhere in Bangkok!
The decor of this open-air restaurant is shabby, but I guess that's part of the experience and has it's own charm.
We saw an elephant perform while sitting there, and off course the usual hawkers, but ignore them and enjoy your dinner.
Favorite Dish: We had a local friend order for us, so I don't know what I ate - chili clams, fried rice, fish cakes... all of it yummy!!!
Her presence might have worked wonders for the service and quality, though - who knows...
if you're looking for ambiance this is not it. but if you're looking for the best authentic food - this is it! i stayed in bkk for 3 days, and it was only in this resto that i had the greatest taste of thai food.
the set up is outdoors with just plastic chairs but you can see a lot of foreigners dining there. what's special about this resto is when it's billing time, the service attendant just estimates the bill. no need for calculator or whatever.
Favorite Dish: everything