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.
We flew from Siem Reap to Koh Samui in 2013. Look into Bangkok Air. I don't recall it being terribly expensive, but was definitelyl the quickest way to go. You'll most likely have a lay-over in Bangkok, but the airport has plenty of shops and restaurants to keep you occupied.