There is no indication that you are sharing the bed with someone else anywhere on the booking or ticket. Also you get dropped off in the middle of nowhere in Sihanoukville and are told to make your own way and pay to get to the port when the bus could easily drop you there
We booked a ticket from Siem Reap to Koh Rong, but when we arrived at Sihanoukville we were just dropped out of the bus with no information. No one of the employees spoke any English, and when a woman arrived that did speak English she was not helpful at all. She told us it was her first day she said she could not help us, but later on she said she did this every day. And even though the employees at Siem Reap told us a transfer from the bus to the boat was included, we eventually had to pay for a tuktuk to take us to the boat. All in all, extremely bad customer service!