What is the best way to get to from Koh Chang, Thailand to Siem Reap, Cambodia? Fastest? Cheapest?
YOU can take a bus or mini van. You also can find the ticket from your hostel or an accommodation where you stay at Koh Chang.
You have to take mini van it will use less time than bus.
I've traveled from Koh Chang to Phnom Penh by bus, but there were options for Siem reap as well and You can purchase it from any agent on the island. It's an all day journey as you have to consider ferry and some delay when crossing the border.