here is an express boat [1] with free transfer from outside Trat Market near the big clock/thermometre. Cost including transfer to the pier at Laem Sok and from the arrival pier at Ko Kut most resorts is 350 baht. About 2 hours. Leaves the market in Trat at 11:30 sharp!
Two speed boats depart daily during the high season from Laem Sok on the mainland near Trat. Stops are made on demand at most west coast piers on Ko Kut, finally terminating at Ko Kut's Bang Bao Bay. First boat departs from Laem Sok at 09:00, costs 600 baht one-way, and takes 60-90 minutes to Ko Kut. Second boat departs at 13:00, costs 600 baht one-way, and also takes 60-90 minutes to Ko Kut. During the low season other operators run a daily service from the Dan Kao pier near Trat city. Two boats depart from Ko Kut daily at 10:30 and 12:00, returning to the mainland