Our last night before departing we went to diner and a show which had traditional Cambodian dances. I’ve been to it previously and still really enjoyed it. The costumes are just so beautiful.
After a 1.5 hour flight from Siem Reap Cambodia, we arrived at the international terminal in Bangkok. As you depart there are signs to go to customs, baggage claim, transfer domestic, transfer international, and the last one is transfer to Koh Samui (among other places). Follow the signs. As a US citizen you are allowed a visa with 30 days and no cost or visa required. If you want to stay longer then you have to either boarder hop or pay the fee.
The Koh Samui Airport is very tiny and has very limited WiFi. We ended up having to pay about $3 per person for a shuttle service to take us to our guest house. Everything worked out in the end. We rented a bungalow right on the beach and it was amazing.