The climb to the final point of view takes about 2 hours and is quite physical but when the weather is clear, the reward at the top is breathtaking. You have a view over the bay and the plain below with its typical karst peaks. At the top, there is a small tongue of stone which has become the place to pose for THE photo that everyone made when coming here (the one I have put to illustrate Tab Kaek Hang Nak trail).Between the road to join the departure of the 3.7 km climb to reach the view, the ascent (2h), the time you will sepnd up there, the descent (1h) and the come back to Krabi or Ao Nang about forty kilometers away, count 6 hours for this visit.
As far as I know, no public transport can take bring you to the starting point of the trek. You will have to go by your own, by renting a scooter (200 THB day + gasoline price) or take a private transport, tuk-tuk or car with driver (count 1500 THB per vehicle because it will probably be a full day work for the driver to bring you there, wait for you and bring you back). Personally, I got there with the yellow tuk-tuk parked in front of the Pack-up Hostel in Krabi Town whose driver knows this trail perfectly (Tel: 086 272 3657 if you want to contact him) but you can of course call to someone else.