That is in the Similan Islands. It is Donald Duck bay on Similan #8. The chain of islands is about 50km offshore from mainland Thailand and is a protected marine park. You can access the islands on a day trip from either Phuket or Khao Lak which is where we stayed.
Here is another shot of the bay taken from where the large rock looks like it's balancing on the hill. The Similans are made of granite and most places have granite boulders stacked on top of each other. One dive site was like that and you could hear the boulders creaking in the waves.
Our home for four nights (the big boat).
