Not so much cities, but towns I like:
Saladan Town Lanta. The seafood restaurants on the water with the pier you are on creaking and moving as you eat.
Khao Lak. Last I was there, there was really only one pub for nightlife, always had a good band, can't remember the name. Great beaches
Krabi Town. Sunset dinner on the river, lots of other really inexpensive eateries in town.