Surat Thani Airport (URT)

Surat Thani International Airport is located nearby (21 km) from the city of the same name Surat Thani and in 80 km from Don Sak Pier, the main transit point for traveling from the airport to Koh Samui, Phangan and Tao.
It is the only airport in southern Thailand serving low-cost airlines. In the case when you need to get to Samui from Bangkok, and then to Phangan from Samui with minimal expenses, you should buy tickets to this ver airport.
But on a bus trip to the ferry crossing, plus the ferry itself, it will take all day. This airport is small and has lack of infrastructure.
Nevertheless, currency exchange, shops, perhaps for car rental in it. If you are on the road to Samui, then go straight to the counter labeled Raja Ferry. There you buy a bus ticket to the ferry and to the ferry itself.
The last ferry leaves at 19.30. The way to pier takes 1.5 hours.