Walking during the tropical heat is poorly tolerated by residents of northern latitudes. Even on a small island you have to use transport. The simplest solution is to call a taxi, but this hits hard on the pockets of vacationers. Much cheaper than renting a bike. Rent will cost from 200 baht per day.
If you decide on a personal vehicle, remember that there are a lot of scammers in the field of motorcycle and car rental on the island.