Flight
There are many daily flights from the International and domestic Airport in Bangkok; Suvarnabhumi Airport (opened in September 2006). Bangkok Air flies direct to Samui Airport. A flight schedule with Bangkok Airways is found here. Thai Airways and Air Asia flies to Suratthani. From there, just catch the bus or taxi to the ferry in Donsak.

Bus
If you want a more economical way to travel, take the VIP bus from the well-known Khao San Road or from the Southern bus terminal at Boromrat Chonnani Road. The VIP buses are more comfortable than the so called A/C bus. You can buy a ticket in almost every travel agency in Bangkok. Ferry is often included in the price.

Train
Another great way to travel is the night train from Hualamphong, the Bangkok railway station, to Suratthani. The sleeping cars are comfortable. It is a little more expensive than the bus, but you will get a good sleep. Upper beds are less expensive than the lower ones. A private "first class" cabin for two persons, is also available.

Ferry
The fastest ferry leaves from the two main piers in Donsak on the main land with operators like Seatran, and Raja Ferry. The price is about 110 baht. You will see many of the small surrounding islands if you don't fall asleep. You might also take the Lomprayah ferry from Chumphon. On smaller ferries (like the Songserm ones) from other piers, you might be contacted by Thai-guys to convince you that "their" resort on Samui is great. It can be a blank or a prize in that "lottery". You can easily book a room or bungalow here 24 hours a day and all year round.