As a matter of fact, we stopped offering the overnight trip from Phuket to Koh Samui, Koh Phangan & Koh Tao because the company that operates it provides bad service in comparison to the day-time trip, we received many complaints from the customers that we booked for this transfer in the past. Here below are the more detailed reasons.
Boat Quality & Safety standards

The night boat to Koh Tao
The night ferry is very old, slow, revamped wooden fishing boat. It cruises all night and reaches Koh Samui / Phangan / Tao at next morning after many hours of navigation, and often gets delayed if the sea conditions are not perfect. For a better understanding of the boat conditions can have a look at this interesting blog post with photos by a traveller that used this service.
Time Schedule
Aside from the low quality and safety standards of the boat, the overnight trip has almost no benefits compared to the day-time transfer also for what concerns the time schedule. The bus in connection with the night boat departs from Phuket Town around 13:00 hrs, which is just a little later than one of the available day-time journeys which departs at 12:30 hrs. The overnight trip can take between 20 and 23 hours (depending on island destination), while with the day-time trip you will reach either Koh Samui or Koh Phangan after just 6-7 hours of travel and arrive on the same day! For Koh Tao, due to the long distance, there is only one day-time transfer daily departing at 10:00 hrs from Phuket and reaching the island at 18:45 hrs.
Road Trip
Another factor to consider is that before getting on the boat at the pier in Surat Thani, there is an approximately 300 km drive from Phuket which must not be underestimated. The road transfers for the overnight trip from Phuket to Koh Samui, Koh Phangan & Koh Tao are operated by an older and often overcrowded bus or minivan which stops many times on the way and still arrives at the pier several hours before the ferry departure (because it transfers other people that have connection with different destinations). The land transfer for the day-time trip instead is done by comfortable and spacious air conditioned bus or minivans, never overcrowded that goes straight to the pier without stops in between (apart from restroom stop at service station) and the waiting time on the pier is minimised as much as possible.
Price
Many people, especially those on a tight budget, would be happy to compromise on all the above cons about the overnight trip if that would help to save some important cash. The thing is that there is little to no difference in price between the day-time and the overnight trip from Phuket to Koh Samui, Koh Phangan & Koh Tao
In summary, we strongly recommend to avoid the overnight trip unless there is no other solution available.
You can find all details about the efficient day-time transfer service HERE, if you have any question please enquire.