Routes
There is no direct boat and there cannot be: Krabi and Koh Samui are on opposite sides of the peninsula, so every route crosses land. The bus and ferry through Donsak is four to five hours and is what most people take.
Bus and ferry
About three hours by coach across the peninsula to Donsak, then the ferry. Considerably shorter than the same crossing from Phuket, because Krabi is already halfway.
Flight
Bangkok Airways flies it direct, but thinly and not all year. Check it exists on your dates before planning around it; the alternative is a connection through Bangkok, which is longer than the bus.
The season changes this. The two ends keep opposite seasons. Krabi is dry December to March and Koh Samui January to September, so the months when both are dry are January, February and March.
These times and fares come from booking agents and route aggregators, not from operator timetables. Most Thai ferry and minivan operators publish no English schedule. Treat every figure as a planning range and confirm it before you build a day around it. Last read on 20 August 2026, from Inside Samui, Krabi to Koh Samui and Direct Ferries, Donsak to Koh Samui.