From Bangkok to Koh Tao

By Air
Fly to Koh Samui and take a bus to the pier and change to ferry or speed boat to reach Koh Tao.

By Bus
Buses for Chumphon leave from Bangkok southern bus terminal.

By Train
Buy a combined train+ferry ticket at Bangkok Hua Lumphong station.
Option 1Take a train from Hua Lamphong to Chumphon and take the ferry from there.

Night trains for Chumphon depart Bangkok Hua Lumphong (arrive Chumphon) at 5.05p.m. (1.27a.m.), 5.35p.m. (2.58a.m.), 6:30p.m. (3.28a.m.), 7.30p.m. (4.23a.m.) and 10.50 p.m. (5.59a.m.)
Ferries depart Chumphon at 7a.m. and 1p.m. Duration of the ferry ride is approximately 1.5 hours.

Option 2 - slower but better connections
Take the train to Surat Thani. It leaves Bangkok at 6.30p.m. and 7.30p.m. Get off the train at Surat Thani railway station. Train arrivals are scheduled at 6.23a.m. and 7.16a.m. respectively. From there shuttle buses (included in the ticket price) take you to the Don Sak ferry terminal. A high-speed catamaran takes you to Koh Tao in around 4.5 hours.