Fastest Option (Most Comfortable)
1) Book an hour flight from Bangkok Airways (call center 1771) or Thai Airlines (call center 02-256 1111) to Koh Samui and buy boat and bus ticket from the airport limousine counter to get to Koh Phangan.
2) Book the flight at Airasia.com (call center 02-515 9999) or Nok Air (call center: 1126) which operate a one hour and ten minutes flights from Bangkok to Surat Thani province daily , buy a boat and bus ticket direct to Koh Phangan from the information counter in Surat Thani airport.
Cheapest Option (But longer...)
1) Buy joint ticket (boat & bus) from any travel agent in Bangkok (especially on Kao San Road) direct to Koh Phangan. The bus leaves from Bangkok at 1800pm and you will be on Koh Phangan about noon time the next day.
2) Buy joint ticket (train & bus & boat) from Bangkok train station direct to Koh Phangan. Train leaves 2-3 times in the evening and you will be on Koh Phangan the next day. website:
Please note - Usually, the bus is available all the time, you do not need to book in advance.
Train on the other hand is always fully booked on the weekend and public holiday. If you choose this transportation, please be aware to book at least 7 days in advance