Ban Bor Thor, about 50 km north of Krabi town, is a small coastal village featuring mangrove forest, rivers, and spectacular limestone caves. This area, which belongs to the Than Bok Khoranee National Park, is one of the earliest sites of human civilizations in Thailand, and you can witness this by seeing cave paintings thousands of years old.
Many of these caves are only accessible by kayak, and you can hire one and have a guide with you in the kayak or not. My wife and I chose to paddle ourselves as we thought it would be more exciting that way, and it sure was a fantastic experience paddle down the river and into the caves. Take a look at the video I recorded below.