Sixteen square kilometres of coconut plantation between Koh Chang and Koh Kood. Two beaches, flat roads, and deliberately very little going on.
Find a room before you go.
Koh Mak sits between its two much bigger neighbours, Koh Chang and Koh Kood, and is nothing like either. It is small, low and almost entirely planted with coconut and rubber, and most of it is still owned by a handful of local families rather than by developers.

The practical result is the thing visitors notice first: the roads are flat. On Koh Chang the hills make cycling a joke; here a bicycle genuinely works, and half the island rides one. The other thing you notice is the quiet — the community has deliberately kept jet skis and loud beach development off the island.
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Ao Kao on the south-west side is where most of the accommodation is: a long, shallow, palm-backed beach with a handful of restaurants and bars strung along it, and the island's best sunsets straight ahead of you.
It is the sensible first choice. There is enough here that you can walk out for dinner and have a real choice, the swimming is easy, and the island's small centre with shops and a couple of dive operations is a short ride away.

Ao Suan Yai on the north-west side is longer and emptier, with a big view across the water to the mountains of Koh Chang. There are fewer places to stay and fewer places to eat, which is exactly the point for some people.
Ao Nid on the east is the working side, with the pier, some mangrove, and boats rather than sunbathers. Ao Pra in the far south-west is the most remote corner of an already remote island. Wherever you stay, distances are small — the whole island is a bicycle ride across.

Ao Kao for most visitors: the widest choice of rooms and restaurants, easy swimming and the sunset. Ao Suan Yai if you want fewer people and a bigger view.
Very. It is small, flat, quiet, with shallow water and almost no traffic — one of the easiest Thai islands to have small children on.
Yes, and it is the best way to see it. The island is flat and the distances are short, which is unusual among Thai islands.
By speedboat or ferry from the piers near Trat, roughly an hour. There are also boats to and from Koh Chang and Koh Kood in high season.
More Koh Mak and eastern Gulf guides, plus the rest of Thailand's islands.