From Tonsai pier it is a twenty to thirty minute walk to the Koh Phi Phi viewpoints. You will climb up the hill that is to the north side of town (also the evacuation route in case of a tsunami). At the entrance to the “park” there will be 20 baht fee per person that goes towards island restoration.
Be sure to walk past the first viewpoint to the second. It is less than five minutes more and offers a much better view.
It is highly recommended to watch the sunrise or sunset from this area. Though anytime is beautiful so long as the skies are clear.