From Bangkok By bus:
Busses go from Ekkamai Eastern Station or MoChit Northern Station. There are buses from Bangkok international airport (Suvaranabhumi) as well, but they are not as frequent.
There is a bus leaving every 1-2 hours from 7am until 11.30pm to Trat Bus Station.
Cost: around 250 Baht for a 5-6 hour trip.
A private taxi should cost 3000-4000 Baht.
There are two flights a day from Suvaranabhumi airport (BKK) to Trat airport (TDX). The flight takes 1 hour and costs 2500- 3000 Baht.
Contact Bangkok Airways, www.bangkokair.com for further information.
Transportation from Trat airport into town (around 35 km) used to be a bit complicated, as the minivans waiting there would mostly go to Koh Chang (around 400 Baht per passenger), and if you wanted to charter them to go to Trat, it would cost around 1200 Baht. But lately there’s a new taxi service that will get you to town for approximately 400 Baht.