Opposite to, say, buses, normally vans do not offer a great variety in the sense of ticket class hence the price of the ticket is the same for all seats in a van. Note that some seats offer more comfort during the ride. E.g. in some vans the passenger seat by the driver is also available. If you are lucky enough to get it, you may have more space and definitely a better view there. Similarly, in some vans seats in the back row may be a disappointment as they do not recline due to the trunk filled with travellers’ luggage.
To hop onto a van between Surat Thani and Koh Samui expect to pay from USD 21.04 to USD 22.72. The more convenient the ride, the more you pay – either for extra space or for less stops enroute. 12Go Transport is the cheapest operator on the route while Raja Ferry (ราชา เฟอร์รี่) is the most expensive one.