Travelling By Ferry : -
 
Ferries and Boats are leaving from various piers, and if they are outside Suratthani, you'll usually have a bus ticket which includes the ferry. There are two Car Ferries, one leaving from Donsak (Raja Ferry) and the other one leaving from Khanom (Songserm Ferry). Both piers are about 70 km outside Suratthani (drive is ~ 1 hour) and are operated throughout the day. The ferry trip takes 1 hour 20 minutes to Samui. The Express Boat leaves from a pier just outside the city, but has a longer way to go and therefore takes about 2.5 hours to get you to Samui (or back). The Night Boats leave from the pier right in the heart of Suratthani. Departure time is 11 pm and the boats are equipped with simple mattresses, so you can stretch out and sleep. They reach the other side at about 5 o'clock in the morning. To sum up, the ferries are fastest and the least expensive, the Express boat and the Night boat are more expensive and take longer ...

Ferry	Timetable Car-Ferry Surat Thani / Koh Samui
Donsak to Samui	08.00	09.00	10.00	11.00	12.00	14.00	16.00	17.00	18.00
Samui to Donsak	07.00	08.00	09.00	10.00	12.00	14.00	15.00	16.00	17.00
Air-condition-bus available for Surat Thani - Koh Samui (using ferry)