Bangkok Oriental, 8043 Ritchie Highway, Pasadena 766-0973. Located inauspiciously in a strip shopping center behind a Denny's, the Bangkok Oriental is a soothing restaurant, with a pretty decor, nice people and richly flavored food. I liked the place and the people who run it. I also liked what I ate, though a newcomer to Thai food. Those whose tastes run largely to Chinese when it comes to Asian food will get a surprising -- and delicious -- sampling of new tastes. We found the wild mushrooms, flavored with sherry, a wonderful beginning and enjoyed the traditional baked shrimp, which was actually a bit bland without the accompanying fish sauce. $$moderate. (Last visited 4/91.)