Flight prices tend to differ dramatically during the year with great Low Season deals on several of the main booking sites. We often use momondo.com for cheap flights.
You can either book your flights just to Bangkok and spend a few days sightseeing, or book direct to Koh Samui, which is only a short ferry ride from Koh Phangan, or Surat Thani on the mainland. If you book your air transfer separately from Bangkok check the links below for prices and schedules. Domestic flights from Bangkok to Koh Samui or Surat Thani take approx 1 hour.
By Air from Bangkok Suvarnabhumi Airport to Koh Samui on Bangkok Air:
BANGKOK AIRWAYS – http://www.bangkokair.com/eng
By Air from Bangkok Don Mueang Domestic Airport (40 min. free shuttle from Suvarnabhumi Airport) to Surat Thani on the Mainland:
AIR ASIA – http://www.airasia.com/th/en/home.page?cid=1
The Bangkok Air flights to Koh Samui are normally more expensive than the Air Asia or Nok Air flights to Surat Thani. However, the journey is a lot quicker as the Koh Samui airport is close to the ferries and the ferry transfers are from 20 minutes to 1 hour to Koh Phangan.
Surat Thani Airport is a 1 hour shuttle bus ride from the ferry port in Donsak and from 2-3 hours ferry transfer to Koh Phangan. There is a lot more waiting around, but the trip is normally a lot cheaper.
If you are booking ferries separately, check out the links below for prices and times. Some of the ferries can be booked online, which is a good option in High Season or around the Full Moon Parties when they are very busy.
By Ferry from Surat Thani Mainland or Koh Samui Airport.
LOMPRAYAH HIGH SPEED FERRY – http://www.lomprayah.com/ww/
SEATRAN FERRY – http://www.seatrandiscovery.com/En/index.html
SONGSERM FERRY – http://www.songserm-expressboat.com/
RAJA FERRY – http://www.rajaferryport.com/index.php?lang=en
Bus or Train from Bangkok
Alternatively, and normally cheaper, you could take a Bus, Train and ferry from Bangkok To Koh Phangan.
We prefer the Government VIP 24 seater bus which leaves from the Bangkok South Bus Terminal. The bus is newly fitted, has a toilet, a hostess on board, plenty of leg room and seat recline to sleep and blankets and meals are included. Bags are safely locked in the luggage hold until you arrive in Koh Phangan. It leaves at around 7.30pm travelling overnight and arriving in Surat Thani ferry terminal early morning. The cost is approx 1200 baht including the ferry and food. There is a 54 seater VIP Government bus which leaves around the same time and is cheaper, but less comfortable.
For more info check the Raja Ferry link – http://www.rajaferryport.com/index.php?lang=en
Lomprayah have a Bus and Ferry joint ticket service which travels during the day.
Check the Lomprayah Ferry link for timetable and prices – http://www.lomprayah.com/ww/
Trains are another cheap way to travel to Surat Thani, then take the ferry to Koh Phangan.
We found a great website which tells you just about everything you need to know about catching the train anywhere in Thailand, including prices, timetables, information about the country, customs and places to go.