This is a hopping spot for a downtown lunch, and no wonder. Diners can buy a heaping plate of two Thai specialties with rice, for almost nothing. A third dish costs a dollar more. The peppy proprietress presides over a cafeteria line and is happy to describe her cooking. Choices change daily, but there are usually at least three vegetarian options and three meaty dishes. The serene blue walls and many tables make the noontime meal seem less hurried.