Koh Kham is a small isle located next to koh Mak and it is the only one comprised of volcanic rock. It has white sand. The beach on the east side is the most outstanding since the sand is very white and black volcanic boulders litter the shore. When the water level reduces, there is a beautiful white sandy ridge separating the sea. To go to Koh Kham, you need to buy a ticket 100 THB+ the boat from koh Mak resort (200 THB total per person), because the isle is private, but it's worth it, the water is so clear, and the sand so white, that it really feels like a paradise island. There's also an abandoned resort on the island which is covered by plants nowadays, a nice spot for photography.