From the Ko Mak pier in Laem Ngop (Trat)
Leelawadee Speedboats  and Panan Speedboats  provide daily speedboat service to Ko Mak, with the last boat leaving for Ko Mak at 16:00. Leelawadee provides service to the Makathanee pier on Ko Mak's south shore, while Panan provides service to the Ko Mak Resort pier on Ko Mak's north shore.
From the Laem Sok pier (Trat)
CP Laem Sok group  provides daily service to Ko Mak's largest pier at Ao Nid, before continuing on to Ko Kut. There was also a once-daily catamaran service between Laem Sok and Ao Nid , which has now been postponed.
Boonsiri High Speed Catamaran  or Koh Kood FantaseaCatamaran  . These two are the same, just different calling. (starting on 15 November 2013) 600 THB per person one way or 1200 baht per person incl. bus transfer from Bangkok. Pick up point in Bangkok is Khao Sarn Road and Shell Gas Station in Bang Na, at 7-8am. Sailing time between 50-60 Minutes. Departures at 2pm. daily from Laem Sok to Koh Mak(Ao Nid Pier) and Koh Kood(Bang Bao Beach), also during low season. free taxi from Trat to the pier in Laem Sok.
From Ko Chang
during the high season there is a twice daily speedboat transfer from Kai Bae beach at 09:00 and 11:00 to the Makathanee pier on Ko Mak. First boat is a sure bet, the 2nd only if there are enough passengers. In the low season this service won't run. On the south end of Ko Chang you can catch either a speedboat or slower wooden boat from Bang Bao.
From Ko Kut
There is 2 boat service. One is once-daily catamaran boat service (Boonsiri High Speed Catamaran ) running from Bang Bao Beach at 11:30, arriving at Koh Mak(Ao Nid Pier) about 30 minutes later. Other one is twice-daily speedboat service running from most resorts that own private piers at 09:30 and 12:00, arriving at Ko Mak about 45 minutes later. These boats typically continue to Ko Chang or the mainland after docking at the Makathanee pier, Ao Nid or Ko Mak pier.
Ko Mak has 27 km coastline, many long sand beaches, a few hills and it is about 16 km² in area.
On low tide, it is possible to walk to Ko Kham ( privately own ), which is a smaller island less than 1 km northwest from Ko Mak. Ko Phi, also north west from Ko Mak but southwest from Ko Kham, is not occupied.
For exploring the island, scooters and bicycles are available for rent at numerous locations, and most beaches and restaurants are within easy walking distance.
Makathanee Resort , +66-(0)878-02757. Has beach front bungalows, pool & sea view hotel rooms at one of the best beaches on the island.
Plub Pla Koh Mak Retreat . Private sea view villas at a secluded location.
Good Time Resort . +66-(0)39-501000. Thai-style resort with pool, spa and tropical gardens.
Thaidaho Vista Resort +66-(0)87.548.2665; email: email@example.com. Non-Smoking Boutique Guest house (only 5 rooms) with spectacular ocean views and tropical garden.
AoPong Resort www.aopong.com; +66907807867; http://www.youtube.com/watch?v=FaheLS5rHO4 ; quiet resort on the private beach with 7 seaview bungalows and restaurant on the beach.
There are daily speedboats from Ko Mak to the mainland, Ko Chang and Ko Kut; slow wooden boats to Ko Chang and the mainland; and daily catamaran service to the mainland.