Bangkok and the BTS Skytrain is convenient for travel over long distances and frequent trips throughout the day.
Koh Chang and its Mu Koh Chang National Park is a nice park and located on the way from the ferry to the White Sand Beach.
Here are the available modes of transport from Bangkok to Koh Chang.
Train Ticket From Bangkok To Koh Chang
Bangkok to Koh Chang is accessible via railway transport by taking the State Railway of Thailand (Southern Line) that hails from the Bangkok Hualamphong station up to the Lang Suan station. From Lang Suan, you can hail a cab that will take you to the city of Koh Chang. The total travel time is nine hours and the fare is US$21. To learn more, visit: http://www.railway.co.th/home/
Bus Ticket From Bangkok To Koh Chang
The distance between Bangkok to Koh Chang is 350 km. Take the Sombat bus when travelling from Bangkok to Koh Chang, then; take the bus that is bound to Ranong. From Ranong, hail a cab that will take you to Koh Chang. The total travel time is 11 hours and costs US$26. For details, check: http://www.sombattour.com/
You can also drive your car; the travel time is 10 hours.
Plane Ticket from Bangkok To Koh Chang
Take the Nok Air flight that is bound to Ranong Airport and from there; take a taxi to Koh Chang. The travel time is one hour and the fare is US$80.