Tucked into a back corner of the West Side Market, this tiny booth overflows with a trove of Cambodian treasure. Pad thai (served with either chicken or shrimp), buckwheat noodles, and egg rolls are served cheerfully by the smiling young proprietor, Sopheap Heng. She's always happy to see you. In fact, she often seems pleasantly surprised to have customers. But lately, she's been getting busy, because the word is out that her food is a steal. Small containers of pad Thai start at just $2, and you can get a big, lunch-sized portion for $4.