The only form of public transportation on Ko Chang is the songtaew. There are about 90 licenced songtaews whose drivers form a co-op. They have a rostering system that ensures equal access to the pier so all drivers receive a fair share of the lucrative fares from piers to accommodation. This means that shorter fares along the west coast are more expensive per kilometre than fares from the pier. Official prices are listed here.
In the daytime, you can catch a songthaew on its route around the main road for 50-200 baht/person (Nov 2022), depending on distance. The rates are generally much higher than in other places, but the vehicles are almost new and in excellent condition. Starting from 17:00, many of them start to ask "taxi" price, telling you that they operate as a public transport only until that time, and may quote prices as high as say 500 baht from Lonely Beach to the Dan Kao pier. However, if you have some time and patience, you still can try and have a "shared" ride with some drivers, maybe for a higher rate if they expect little or no other passengers. There is no service between 01:00 and 07:00.
These taxis are also waiting at the Dan Kao Pier (50 baht/person to White Sand Beach, 100 baht to Lonely Beach). At the Dan Kao Ferry Pier there may be no taxis available. If you arrive without a vehicle you may have to walk the 400 m to Dan Kao Pier.
Most hotels can also organise a rental car for you. A four wheel drive is recommended, since some roads are in bad condition, especially near Lonely Beach.
If there are 2 or more people going with you, hiring a songthaew may cost the same price, or even be cheaper than paying per each person in a "shared" songthaew (there is no difference, an empty songthaew can easily be hired). Just do not forget to bargain if their price sounds quite silly when compared, say, to Bangkok taxi-meter (on Ko Chang, it can be difficult if not impossible to get the same price, but you should not have to pay double). Most folks however, just stay put on the beach of their choice and walk to wherever they want to go.
Hitching on Ko Chang is also an alternative if you choose not to pay the often exorbitant fees of the songthaew. Many islanders are more than willing to pick up a hitchhiker who happens to be going the same way they are. A Coke or cold bottle of green tea for the driver are always appreciated at the end of your journey.
Motorbikes are a fantastic way to explore the island. Small motorcycles can be hired for 150-250 baht per day. The main road is sealed and almost circles the island and there are plans to complete the circuit in the near future. The eastern road leading all the way to the War Memorial, at the island's southeasternmost point, is worth a trip.
Riding a motorbike is not for the inexperienced or faint of heart. Most visitors manage on level roads, during the daytime and during good weather conditions. Darkness and rain, together with poor skills, steep hills and questionable maintenance can be fatal. Statistics vary, but numbers of arround one death / day during high season are not unheard of. Think twice if you have to travel at night, and when it rains during the night, avoid the steep hills in the north and the southwest. The east coast has far less traffic, but that doesn't mean it's safer.
When renting a bike, check tires, brakes, lights and mirrors. Engine must stop when extending the side stand. Reputable shops will fix and issues while you wait. Even better, good rental shops only display bikes that are in top condition. There are a lot of rental shops which take this serious, so pick one of them. Don't compromise on safety. Bring your own helmet if you have one. Every rental place provides helmets, but these provide limited protection.
Anti-lock braking (ABS) is getting more and more common with mid-range bikes. If you can, get a bike with ABS. The ABS indicator light will be lit after start and will turn off when starting driving. If not, something is off.
Use maximum caution when riding. Don't get complacent, even if you are used to driving bigger bikes in your home country. There might be surprises at any time, from any direction. As you are not wearing any protective clothing, going over 30 km/h might not be a good idea. Don't match the speed of the locals. The first rain after a dry period is the most dangerous time. Avoid the roads until the slippery stuff has washed of. The sharp curve right after Siam Bay resort (painted red) should be completely avoided in this case.