Long ago, before Lower Greenville Avenue became a spectator sport forum where neighborhood activists sparred with bar owners over awnings and patron pissings, Thai Soon was making Dallas safe for exotic Asian cuisines. That's why when the Lower Greenville drama got too thick several years ago, it headed north to Richardson along with its drinkless emphasis on vegetarian, seafood and chicken Thai renderings. Over the years, exotic Asian cuisines have almost become routine in Dallas, and Thai Soon's creations often seem rough around the edges. But that doesn't mean you should attempt to skip the vegetarian spring rolls, the panang curry or the Tom yum spicy hot sour soup. You just shouldn't. That would be as tasteless as a Lower Greenville lawn whizzer.