Quiet coast to holiday island: ride the southern line to a pier, pick your boat, and let the Gulf do the rest.
Find a room before you go.
From Ban Krut the Chumphon catamaran route is shorter and prettier, island-hopping via Koh Tao and Koh Phangan to Samui. The Surat Thani route takes longer but runs bigger, steadier boats and more departures - the better bet in the rough months.

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Early train south, then Lomprayah across - about 4 hours on the water with the island stops. Watch the Gulf turn bluer the further south you get.
Longer on the train, then the joined-up bus and big Donsak car ferry. More daily options and the calm-water choice.
Driving down? Raja's car ferries from Donsak take vehicles across all day - park-and-sail also works from the Chumphon piers.
Step-by-step transport guides for this stretch of the Gulf coast.