Honestly, if you haven't been here yet, you're doing something wrong. The food is cheap- and good.
Getting a table here with a group can be a problem on the weekend because they don't take reservations, so come early or eat late. The menu is small enough that you'll be able to decide what you want pretty quickly, and it's hard to go wrong. My personal favorite is the Sukothai, a lighter alternative to most of the other dishes on the menu. The noodle soup is topped with bean sprouts, an egg, some vegetables, and crispy wonton strips, and is the perfect dish for a cold winter day. If you're feeling more traditional, the Pad Kee Mao and the Chiang Mai Curry are both delicious dishes that are a little more hearty.