Bangkok to Koh Samet

Cherdchai Tour runs the bus from the Eastern Bus Terminal at Ekkamai, next to BTS Ekkamai, straight to Ban Phe, with departures at 07:00, 09:00 and 11:00. The fare is about ฿190, the ride takes 3 to 4 hours, and it ends at Nuan Thip pier, where the ferry counters are, so you walk off the bus and onto a boat. Coming back, the buses leave Ban Phe at 12:00 and 14:00.

Outside those times, vans to Ban Phe leave from Bangkok's bus terminals (the old vans at Victory Monument were moved to the terminals in 2016), and the combined tickets sold on 12Go and in Khao San travel agencies put you on a bus or van in the morning with the boat to the island included, for about ฿350 to ฿670. They're the simplest choice if you'd rather not buy two tickets.

Ban Phe has several piers, and Nuan Thip is the main one. The wooden ferries run roughly hourly through the day to Na Dan, the island's main pier in the north, and take about 40 minutes for about ฿50 to ฿70 one way or ฿100 to ฿120 return. Speedboats cross in about 15 minutes, as a shared seat for about ฿200 to Sai Kaew and up to ฿500 to the beaches further south, or as a private charter for ฿1,800 to ฿3,000 depending on where you're going.

The ferry is fine for Sai Kaew, Ao Phai and anywhere near Na Dan. If your hotel is on Ao Wong Duean, Ao Prao or further south, a speedboat straight to that beach saves a bumpy songthaew ride across the island. Boats start in the morning and the last ferries leave in the late afternoon, so on a late bus, plan on a speedboat or a night in Ban Phe.

When you land, foreigners pay the ฿200 national park fee (฿100 for children) in cash at the checkpoint past Na Dan pier. Songthaews wait at the pier, about ฿20 to ฿60 a person shared to Sai Kaew and Ao Phai, and ฿200 to ฿600 to charter one to the southern beaches.

Ban Phe is about 186 km from Ekkamai and 177 km from Suvarnabhumi, roughly two and a quarter hours by car. On 12Go, cars from central Bangkok or either airport to Na Dan pier with the boat included start at about ฿3,000 with a speedboat and about ฿3,400 for a sedan with a seat on the shared ferry, which is the easy way to do it with children or bags. A family arriving at Suvarnabhumi can be on the island about three hours after leaving the airport.

Going back, the ferries leave Na Dan through the day, and the Cherdchai buses leave Ban Phe for Ekkamai at 12:00 and 14:00, so the late-morning boat is the one to catch. Combined boat-and-bus tickets back to Bangkok and the airports sell on 12Go and at the travel desks on the island.

For a flight, a car from Na Dan pier with the boat included is the safe choice, about three hours to Suvarnabhumi. I'd leave the island at least six hours before an international flight.