's mostly people power. The islands are small enough that you can walk, although to get to some of the more far-flung destinations a bike will be nice. They can be rented everywhere, typically for 10.000 kip (€ 1) per day. If you're feeling super-lazy, you can rent motorbikes from around 70,000 per day in many locations on Si Phan Don, passport required. The road in Don Det is very rutted and muddy so one should take caution, either on a bike or motorbike. Once one leaves Don Det town, the road is much better and one can ride as fast as one wishes.