Thanks for the help everyone, mission accomplished!

USM customs inbound was barely noticeable, and outbound non-existent. A simple resort style airport.

The Thai customs website is unclear so I did not declare it with the hope that I could argue about this if stopped, but brought a "receipt" with me to be on the safe side. On the way out my fiancee wore it so it wasn't a problem

OT, Koh Samui is a wonderful place.