When looking for a great place to eat Insert-Name-of-Cuisine-Here, people have all sorts of systems. They look at the neighborhoods and the crowds, read the menu, talk to the owners. But for a quick bit of gastronaut shorthand, one can always look to a restaurant's history: How and, more important, why did it get started in the first place? In the case of Bai Tong, the story is just about perfect. It began as a Thai restaurant operating out of a motel that catered almost exclusively to Thai Airways flight crews looking for a taste of home when stranded far away. Over the years, Bai Tong has moved, expanded, and become more accessible to more people. But its core?the unbelievably good menu full of seriously authentic Thai goodness?has remained more or less the same. The only real change has been how popular the place has become, enough so that it can be tough to get a table during the hungriest parts of the day. ?Jason Sheehan 16876 Southcenter Pkwy., Tukwila, 575-3366