The Koh Chang Ferry operates between Ao Thammachat Pier on the mainland and Ao Sapparot Pier on Koh Chang. The first ferry departs at 6:30 AM, and the last one leaves at 6:30 PM. Ferries run hourly throughout the day, but during busy periods, they increase to every 20 to 30 minutes to reduce waiting times.
When you arrive at the pier, you can easily purchase your tickets on-site. The cost for a one-way ticket is 90 THB for adults, while children can travel for 40 THB, or even free depending on their height.

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

From Bangkok: Direct (mini)buses depart throughout the day from Ekkamai Bus Station. The trip takes approximately 7 – 8 hours. Buses either go to Trat Bus Station or directly to the Koh Chang Ferry. You shouldn’t leave Bangkok later than 1 PM to ensure you catch the last ferry to Koh Chang.

If you book a tourist bus through a local tour agent, there are several pick-up points in Bangkok, or you can request a hotel pick-up. Tourist buses will drop you off either at Koh Chang Ferry or directly at your hotel on Koh Chang.
You can also book a bus yourself online with Boonsiri, please check: https://boonsiriferry.com/en

On Koh Chang it is possible to book direct buses to Bangkok, Koh Samet, Pataya and into Cambodia.

A private taxi from Bangkok to Koh Chang takes approximately 6 to 7 hours. Prices range from 3,500 THB to 5,000 THB, depending on the number of passengers and the pick-up location in Bangkok. It’s a very comfortable option, allowing you to leave and to take breaks whenever you like, and it will take you directly from your hotel in Bangkok to Oasis Koh Chang.

Bangkok Airways operates daily flights between Suvarnabhumi International Airport (Bangkok) and Trat Airport (Trat). For flight schedules and prices, visit the Bangkok Airways website.
https://www.bangkokair.com/

Trat Airport is about a 20-minute drive from the Koh Chang Ferry. There is a minivan shuttle service that can take you directly from Trat Airport to your hotel on Koh Chang for 950 THB per person. No need to book in advance—tickets can be purchased on arrival.