Surat Thani is the other main port to come to Koh Tao. However, if you don’t like traveling with the night boat, be prepared for a 6 hour day boat journey.
Both Lomprayah and Seatran companies offer day time ferries from Surat Thani to Koh Tao. Seatran departs Surat Thani at 8am arriving on Koh Tao around 15:00pm. Lomprayah has 2 departure times. One departs at 8am and arrives on Koh Tao at 14:30pm, the other departs at 15:30pm and arrives around 19:00pm. (please make sure your accommodation on Koh Tao is reserved and they know you are arriving on the late Lomprayah as many receptions close around 17:00 to 18:00pm)
The nightboat leaves daily around 23.00 pm and arrives on Koh Tao the next day around 6.30 am. The boat has sleeping facilities but this doesn’t involve much more than a small pillow and a thin matrass.
The nightboat has its charm and is an easy way to travel "fast" even comfortable if you are prepared to accepts its limitations.
Tickets for Lomprayah, Seatran and the nightboat ferries to Koh Tao can be bought in one of the numerous travel agency you will find in Surat Thani.