When Kris Yenbamroong was in junior high in Thailand, he went to an exclusive private school. But somehow, he says, he always found himself eating lunch not with his well-heeled classmates but with the groundskeepers and maintenance guys. It's a perspective that has come to define his cooking.Yenbamroong, from a four-generation restaurant family, is the chef at Night + Market and Night + Market Song, which both specialize in rough-edged Thai country food, cooked with a modern sensibility.One…