Thailand's most famous soup is tom yum, a spicy sour broth with various delicious things floating in it. Often it's seafood, like shrimp or squid, but it could contain pork or chicken instead. When I came to Vietnam, I was suprised that they didn't have more Thai or Cambodian restuarants. I discovered that they did recognize their neighbour's food, but they served them in Vietnamese restuarants, alongside thier own dishes. Bún thái is Vietnam's version of tom yum. The broth is fairly similar, depending where you go and it always contains rice noodles. Vegetarians, watch for the supposedly meat free version bun thai chay.