Khao Ngon Nak is also known as Dragon's Crest Mountain which is situated in Krabi. Admission is absolutely free, but giving donations is highly appreciated. From Ao Nang or Krabi Town you can rent a tuk-tuk which is a bit pricey, some hotels and travel agencies offer day tours and it would cost you around 700 baht per person and up. I highly recommend renting a motorbike for about 200-300 baht per 24hrs. Once you arrive at the registration, the officer will orient you about what to do's and dont's while in the national park. They will give contact numbers too, just in case you need one.