Krabi remains one of my fav places but why not try visiting islands like Koh rok, koh mook where the emerald cave is located. Swimming through the cave into the beach enclosed in the island is a great experienece.
This is the entrance to the emerald cave
Also went for a hike in the trang region, Quite a number of waterfalls and also visited the sakai people

Very much less touristy down south in the trang area.
Enjoy atheris !