Most of you will come from abroad and arrive at Suvarnabhumi International Airport in Bangkok. You will then go directly to Koh Chang or take the opportunity to visit Bangkok and spend few days there.
There are 3 different ways to go to Koh Chang, by plane, by car or by bus. The safest but not always the fastest is the plane, then comes the car with a private driver and at last the cheapest and slowest is the bus.
If you are coming from other parts of Thailand like Phuket, Chiang Mai, Koh Samui or Udon Thani, there are also direct flights to Trat. Check with Bangkok Airways!
Think about Private Transfers, they could be a very good alternative if you are travelling with your friends or family. It's cheaper than several plane tickets and depending of your transit time at the airport, Private Transfers can be as fast or even faster than a plane. Look at this article, it may interest you: Transfers from and to Koh Chang
If you have any questions or want more information, feel free to contact me!