Koh Samui Location

Koh Samui is situated in the gulf of Thailand, about 650 Km South of Bangkok .
There are many ways to reach the island:

BY AIRPLANE:

The airline which serve Koh Samui is Bangkok Airways. It flies directly from Bangkok to Samui several times a day.
from Singapore and Phuket to Samui twice a Day.
from Utapao ( Pattaya ) to Samui daily
from Krabi to Samui 4 times a week ( Monday, Wedsday, Friday and Sunday )

Thai Airways flies from Bangkok to Suratthani twice a day

Berjaya Air flies from Kuala Lumpur to Koh Samui twice a week ( Thursday and Sunday )

Detailed flights tickets information

BY TRAIN:

There are daily trains leaving Bangkok in the evening and arrive Suratthani early in the morning, from there there is in connection with the Express boat by Songserm or the car ferris by Seatran and Raja Ferry which will take you to Nathon Pier in Samui.
Seatran is the most comfortable and safe transportation by sea, at Seatran website you will find all the details how to get the boat from Suratthani airport, train and bus stations.

There is also one train which is coming from Singapore, Kuala Lumpur and Penang arrive Suratthani in the evening; At that time you will not be able to catch the ferry boat until the next morning unless you take the sleeping boat which leave Suratthani night market at 9pm and arrive Samui at 5am.
Usually join tickets Train-Boat are for sell in every travel agency around Thailand.

BY BUS:

There are many companies which provide Bus service from Bangkok to Samui. They generally leave Bangkok in the evening and arrive in Suratthani the next early morning; from there there is in connection with the Express boat by Songserm or the car ferris by Seatran and Raja Ferry which will take you to Nathon Pier in Samui.
Seatran is the most comfortable and safe transportation by sea, at Seatran website you will find all the details how to get the boat from Suratthani airport, train and bus stations.

Also there are daily Buses from Phuket, Kraby and Hat Yai. They all leave in the morning and arrive in Samui in the afternoon or evening of the same day.