Mu Ko Ang Thong National Park is a stunning archipelago of 42 islands in the Gulf of Thailand. It's known for its rugged limestone hills, caves, and emerald saltwater lakes. It is only accessible by boat and tours offer snorkeling, kayaking, paddle-boarding, and hiking.
If you are up for the challenge, there is a panoramic vista of the islands once you hike up to Wua Ta Lap viewpoint. I highly recommend this because you can see the archipelago from above and the scope of it all is extremely impressive.