If you want a really good, inexpensive Thai meal in Chicago, you'll love this place. It's a medium cab ride from downtown, and cabs are usually plentiful by the time you've finished up.
P.S. Bangkok 2
2521 N. Halsted Street
Chicago, IL 60614
Make sure you go to P.S. Bangkok 2, not P.S Bangkok. (P.S. Bangkok is run by a sibling of the owner of P.S. Bangkok 2. It has more elaborate decor, but in my opinion, the food is not quite as good.)
I moved to Seattle 6 1/2 years ago, but I still go back to P.S. Bangkok 2 at least twice every single time I make it back to Chicago (usually straight from the airport). My friends have FedExed me their pad thai for my birthday (really).
Things you should try:
Above all else
 Pad Thai like none other I have ever had. Get it crispy, and dont bother to get meat with it. It doesnt need it. Take the leftovers home its great cold the next day. (I always order an extra order at the end of the meal if it looks like there won't be enough for breakfast. :))
 Steamed dumplings they look like little jellyfish, only much tastier.
 Spiced dumplings
 Bombai Delight
 Fruit Lovers Salad
 Banana Blossom Salad
As for other selections, I have yet to have a bad meal there. Everything has been well prepared with a nice balance of flavors. They have a good selection of curries. They have a wider variety of appetizers and salads than I have seen at other Thai restaurants.
Hope you enjoy it! Tell them the tall blonde lady from Seattle sent you.