Chanthorn Phochana, on Benchamarachuthit Road just south of the centre, is the obvious place to try pad senchan — the city's signature dish of springy local rice noodles stir-fried with prawns, egg, garlic, and a touch of soy sweetened with palm sugar. Order it the dry way, not the wet one, and ask for it spicy.
The restaurant is large, brightly lit, and crowded with families at lunchtime. The menu runs to a hundred items but the noodle dishes are what they do best. Cheap.