To and From Bangkok
Ko Lanta is about 1000 km. far from Bangkok. Which you can travel by flight, train or air-con bus.

If you're flying into Bangkok try to get a connecting flight to Krabi, the closest airport to Ko Lanta. Second choice is Trang and third choice is Phuket.

If you want to travel by train you can buy the ticket to only Trang Provience. From Trang you can get the air-con minivan to Ko Lanta at the oporsite Trang train station.

Alternatively, You can take overnight 24 seats air-con bus to Krabi directly. The bus will depart from Bangkok around 17:00 and arrived to Krabi at 5:30 am. There is no ticket advance system. You need to go toSouthern Bus Station (Sai Tai) at upskirt of Bangkok.