There is one main road running North to South on the island with many smaller roads diverting off it. Some roads lead over the spine of small mountains that run along the middle of the island and are all dirt, can close out after rain, and can be challenging even to a skilled driver. If you are looking for an adventure the dirt roads are a good place to find it, also be aware distances can be quite deceiving due to the quality and elevation changes of the trail. There are usually plenty of taxi cars available on both Sairee village and Mae Haad, however they tend to be expensive given the actual distance you travel. The best way to travel is by renting a small scooter or motorcycle. This gives you the freedom to explore all of the treasures of the island without paying the large taxi costs.
You can rent bicycles and motorcycles at a few places on Sairee Beach, Mae Haad, and Chalok. Be careful if you rent a motorbike as the dirt roads can get dangerous. ATV's all terrain vehicles are dangerous ask any medical clinic and expensive 500+ baht/day and should be avoided in favour of Honda Dream's 150-200 baht/day or Sonic's 200-250 baht/day.
It is normal practice for motorcycle rental places to ask for a passport as deposit, this is due to the fear of drunken tourists crashing their bike and not returning it. You should be wary of handing over your passport unless you are positive of the legitimacy of the operation.
Be aware that an increasing number of rental shops are charging large amounts of money for non-existent scratches on bikes when returning them, notably the shop next to 7/11 in Sairee Village Save Way travel and Owen Bikes opposite the petrol station in Sairee Beach. Make sure you note down and photograph all scratches and dents before you rent a bike from anyone. Your best bet is to hire a bike from your bungalow / resort.
Longtail boats offer rides to and from certain beaches on the island. They are a more comfortable way of getting to isolated beaches than attempting to ride over the mountains, however they are noisy. Round island longtail can be as much as 2,000 baht, whereas some short trips will only be 100-200 baht.