Travel by Plane, Bus or Ferry from Bangkok to Koh Samui
From Bangkok to Koh Samui By Plane – The most expensive, but best by choice
This is the fastest way to get to Koh Samui, but at the same time it's the most expensive option.
Samui International Airport (USM) also known as Koh Samui Airport is located aproximatelly 2 km north of the largest city on the island, Chaweng. From there, there a lot of transportation options all accross the island as shuttle buses, taxis or rent-a-car venues.
There are cheaper low cost airlines operating this route (Nok Air & Air Asia) but the flight isn't direct and they require a ferry transfer, but in case of having a problem, or in need of a date change, you won't get a refund for your air ticket.
From Bangkok to Koh Samui by Train and Ferry - The Middle Option
One of the cheapest alternatives is to take the overnight train from Bangkok to Surat Thani as Thailand has on the best rail systems in the world offering an affordable possibility to see the Thai countryside landscape.
After arriving in Surat Thani you should catch the ferry to Koh Samui. A train ticket from Bangkok to Surat Thani costs about $50. You can find more info on fares and the train-ferry connections here.
From Bangkok to Koh Samui by Bus-Ferry – The Cheapest Option
Although this is the cheapest alternative to travel from Bangkok to Koh Samui, the travel time will take up to 12 hours but it will only cost you about $35. You can hop directly on one the buses that leave Bangkok Central Bus station towards Surat Thani each hour.
This option doesn't require a pre-arranged reservation. There are some bus travel services that include the ferry transfer in the ticket's price, so you don't have to worry about the bus-ferry transfer.
There are two types of buses that run on the route towards Koh Samui,
The ride will take up to 10-12 hours and they ussually leave Bangkok between 5:30 and 8:00 in the evening, thus travelling 470 miles by night.