Well, BA is not known for good ethnic foods, so don't get your hopes up too high. That said, there are a lot more options now than when I arrived.
Lotus Neo Thai is supposed to be pretty good (in Barrio Chino, heard good things from friends) but I've never been there. $$
Sud Estada is tasty pan asian food, but also pricey at night. Their lunch menu is good.
Lastly, Cocina Sunae a puerta cerrada that changes its menu weekly has yummy thai when they serve it. I've tried her panang curry and pad thai and both were delicious. She has a price fixe menu that is a pretty good deal and includes appetizer, entree, and something to drink (I think!).
Me, I mostly try my hand at home since eating "exotic" food out here kills my budget. Love Barrio Chino!