There are 2 different ferries to / from Koh Chang; the Koh Chang Ferry and the Centrepoint Ferry.

The Koh Chang Ferry runs between Ao Thammachat (main land) and Ao Sapparot (island), takes about 35 minutes and cost 80 Baht per person one way.

The Centrepoint Ferry runs between Ao Centrepoint (main land) and Ao Dan Kao (Island), takes about 60 minutes and cost 50 Baht per person one way.

Both ferries run daily between 7 am and 7 pm.

For more information and timetables check http://www.kohchangferry.com/

There are several (mini)buses from/to Koh Chang.

From Bangkok there are direct (mini)buses leaving from Ekkamai Bus station and Suvarnabhumi International Airport. You can buy a ticket on arrival; the buses run daily from early morning until around 2 pm.
If you book a bus ticket at one of the local tour agents in Bangkok, you get picked up at your hotel and dropped off at one of the ferries to Koh Chang.
Prices differ depending on type of bus and if you get picked up or not. You shouldn’t pay more then 900 Baht per person one way.

On the island you can book direct (mini)buses to Bangkok, Ban Phe (Koh Samet), Pattaya, Siem Reap (Cambodia), Sihanoukville (Cambodia), Koh Kong (Cambodia), Pnom Phen (Cambodia) and visa-run.

A private car (max. 3 persons) with driver between Oasis Koh Chang and Suvarnabhumi International Airport Bangkok cost about 3.500 Baht and between Oasis Koh Chang and the center of Bangkok cost about 4.000 Baht.
A private minibus (max. 8 persons) with driver between Oasis Koh Chang and Suvarnabhumi International Airport Bangkok cost about 5.000 Baht and between Oasis Koh Chang and the center of Bangkok cost about 5.500 Baht.
For more information, up-to-date prices or booking, please contact us.

Bangkok Airways operate daily flights between Bangkok and Trat, the flight takes about one hour. Check their website for flight schedule and prices:

http://www.bangkokair.com/