Having tried most if not all of the Thai places in Faifax, my pick is Pad Thai. Unoriginal name, but they have the most authentic Thai food in the area. Of course the pad thai is good, but my current favorite is their Drunken Noodles. Also, their chef will cook you anything you want; so if you've been to Thailand and can't get your favorite dish anywhere else (or everywhere else sucks it up), try here.
is on Lee Hwy near where Jermantown hits. (a few blocks West of the rt50/lee hwy intersection). It's in a little strip across from Kmart nestled between Arigato Sushi and Blimpie Subs. They also deliver.