Krabi and Trang are Ko Lanta's closest airports and there are regular public minibuses and private taxis that service these routes.

There are also ferries and speedboat that run between Ko Lanta, Krabi, Phi Phi Island, Lipe and Phuket is the public passenger ferry that runs November to May. No ferry service is available from Trang.
The easy way is public minibus service is also available between Krabi, Trang, Phuket and Ko Lanta. Public minibuses are available daily from mid morning through mid afternoon.

For traveler come up from Malaysia or Hat Yai or take train down from Bangkok, Trang is only the access point to Ko Lanta with the distance about 140 kilometers and takes approximately 2 hours by minivan. A public minivan service operates throughout the year, with buses leaving daily during 10:00 to 15:30 on every one hour. The minivan station is within a tour office opposite the train station.

If you’re coming under your own steam, you’ll need to use the vehicle ferries between Ban Hua Hin and Ban Khlong Mak (Ko Lanta Noi) and on to Ko Lanta Yai. These run frequently between 6:30am - 10:00pm every day throughout the year.