After noticing a listing in one of those coupon books, I tried Thai Heaven a couple nights ago. It's a very tiny hole in the wall on the east end (literally - it doesn't face the street) of a strip mall on the south side of the street, just a block or two *inside* the Baltimore beltway on Frederick Road.
Absolutely zero points for decor (it looks like a bottom tier carry out place from the outside), but the staff are friendly and the food is inexpensive and pretty darned good. It's not the sort of place one would go for a fancy Thai meal or to impress a date (unless said date is a hard-core Hound!), but if you're on the west side of Baltimore, you've got a jones for no-frills Thai, and you don't want to drive too far, it's a nice option to know about, and one that a person would be unlikely to stumble upon if one were not specifically looking for it.