One of my favorite spots in the Andaman Sea is Ko Haa between Phi Phi and Lanta. There is quite an abundance of cliff-face that makes for wonderful macro ops. It's the first place I ever saw a Ghost Pipefish. It was hanging out by a huge sea fan for almost every dive. Sad to say last time I was out to Ko Haa the Pipefish was gone, but at least the sea fan is still there!