Of all backpackers hostel that I ever been, Pak Up Hostel in Krabi, Thailand was the best, ever! But take note, that was in 2012, it might changed nowadays. It is hard to maintain a hostel, you know?
220THB per night, that was pretty cheap for a 5* hostel. Large, solid wood bunk beds (I stayed in 8 beds dormitory, on upper bunk and a person below told me she didn’t feel anything when I go up or down from the upper bunk), good material for bed sheet, pillow case and duvet (yes, duvet!) – almost like cashmere. Clean, spacious toilets and bathrooms with hot/cold showers. Shampoo, shower gel also provided in dispenser. Wire line to hang your wet clothes after wash it in DIY washing machine and if you wanna make it quick, they also have 3 dryers. Internet connection pretty fast too. They also have rooftop bar and live one-man show during my stay.
Free advertisement? Well, yeah because Pak Up was really worth every single penny spent! Although it is in the town, not in Ao Nang or Railey, but it never been a problem for me. Just cross the road and get the pick-up van/lorry (worked fine just like a bus) for very cheap fare.