It should drop you off on the island. To Samui, Busses usually stay on the boat, although you are allowed to get off. Youll then drive 100 meters off the ferry to an unloading zone.....
From Koh Tao, that's debatable. Since no bus actually leaves from koh tao, best to say ticket is not included for ferry. From places like KPG and Samui, the boat ticket is included, although you quickly see they are ripping you off, charging you full boat fare despite it being one vehicle...
For Koh Tao, busses are leaving from Chumphon. So you must first get to the Chumphon terminal...plan on 100 baht for this, or when buying the ferry ticket, you will have the option of buying boat only, boat to bus terminal, boat to train terminal, boat to airport etc etc.. For you then, you'd do boat to bus...Best if you already have the bus ticket before hand!!! Super VIP busses are very nice and usually include food, which they may or may not tell you!
FYI, Lompraya has a pretty good all inclusive that you might consider...... For that, it'll be boat, bus will meet you, and direct up to bangkok dropping you at Baglamphu post office just outside kho sarn road area!