The Khao Lak region is about 12.5 miles long, so that leaves room for a wide variety of methods of travel. It's important to remember, however, that it's a collection of separate villages that are spread apart, so it's not exactly built for pedestrians. Additionally, the roads can be quite dangerous for the inexperienced, as local police tend to be lax about speed limits. Because the region is difficult to navigate by self-driving or walking and there is no bus system, taxis are among the most efficient ways to get around.
There is no underground in Khao Lak, and the closest train of any kind is about 124 miles away.
Taxi and ride-hailing apps
Taxis dominate the transport options in this region. They can come in many different forms but are predominantly either motorbikes or songthaews, which are converted pickup trucks. If you have a large group, a songthaew is essentially your only option. Ride-hailing apps like Uber don't operate in Thailand, but Grab does. You may not find anything as far out as Khao Lak, however, so taxis may be your only option.
There is no bus network to get you around the area. Any buses you see are to get in and out of the region rather than to travel within it.
Car hire is available, though they're not all that prominent throughout the region. Instead, you'll find plenty of motorbikes available for hire. As long as you have a valid driving licence and an international driver's permit, you can hire one for yourself. Just keep in mind that they can be hard to control for people without experience, so give a motorbike a test run in a car park or quiet road before taking it out properly.
If you're interested in a bicycle without a motor, that's available as well. They can be great for getting around individual villages, but it'll be a significant workout to take a bicycle throughout the entire 12.5-mile length of the region.