This archipelago is probably the best kept secret in south Thailand. With great beaches and not only on every island, there are over 50, but also around 30 km along the coast starting at Pak Meng. That is the most famous beach and is about 15 km west of the city. Most famous islands are Ko Mook (Muk) with the Emerald Cave, Koh Kradan and Libong a bit further north, already in Krabi province is Koh Lanta.
The Trang hotel in the city is low priced, around Baht 700,- and an ideal starting point since the tourist office is just around the corner and the travel agent in the place is very efficient. There is some other accommodation available and even a bit of nightlife.
The real exotic beaches in the warm tropical waters of the Andaman Sea are on the islands, there are amazingly low priced resorts there. Ideal places to relax, eat seafood, lay in the sand and do nothing, if you like.
But there are, again if you like, plenty of things to do, probably the most interesting tour and day trip is exploring the Morakot or Emerald Cave, a stunning limestone cave with all "bells and whistles".