Flights straight to Samui's own airport run famously pricey, since one airline dominates the route. The classic backpacker routes still work: bus, train, or a cheap flight to Surat Thani, then a 1.5–2 hour ferry from Donsak pier. Here's every combo with fares and times, so you can choose before you book.
There's no bridge to Koh Samui — if you don't fly, you take a boat, and the big ferries leave from Donsak pier in Surat Thani province, about 60–70 km east of Surat Thani town, its train station and its airport (another 1–1.5 hours by road). It sounds fiddly, but in practice it's easy: Thailand has been selling joint "through-tickets" on this route for decades. Buy one ticket from Bangkok or Surat Thani and the buses and boats hand you along until you step off on the island. Note there's no train or metro on Samui itself — the nearest railway station is Surat Thani on the mainland — so the plan is just two parts: how you reach the coast, and which boat you board.
The big ferry port on Surat Thani's eastern coast. Raja Ferry and Seatran Ferry vehicle ferries alternate sailings through the day, crossing to Samui in roughly 1.5–2 hours, carrying both walk-on passengers and cars or motorbikes. Most bus+ferry combo tickets board here.
The heart of reaching Samui on a budget is the joint ticket — an overnight coach from Bangkok to the pier, a sleeper train to Phun Phin then bus+ferry, or a low-cost flight to Surat Thani (URT) followed by bus+ferry. Every formula ends at a pier on the island's west coast (Nathon or Lipa Noi), with a short road transfer to the beaches.
Every formula ends on the same ferry deck; what differs is the overland leg. Pick by budget, time and temperament.
The three main names differ in speed, price and which pier they land at — knowing this before you buy makes the onward transfer much easier to plan.
Your combo ticket usually names the boat you'll be on. The detail that matters most is the arrival pier on Samui — Raja lands at Lipa Noi (a little south of Nathon), while Seatran lands near Nathon; both are on the island's west coast, with a 45 minute–1 hour road transfer to Chaweng or Lamai. Lomprayah is a different animal: a fast catamaran running the Chumphon–Koh Tao–Koh Phangan–Samui line, ideal if you're island-hopping.
The big name of the Gulf islands, linking Chumphon, Koh Tao, Koh Phangan and Samui, and selling through bus+boat tickets from Bangkok (usually a morning and an evening departure). Quicker than the big ferries but pricier, and rockier on rough days. Its Samui pier is generally Nathon — double-check the pier printed on your ticket.
A large vehicle ferry sailing Donsak ↔ Samui roughly hourly through the day, taking about 1.5 hours, with an air-con lounge and open decks. It docks at the Seatran pier near Nathon, and a large share of combo tickets use it. Steadier than the catamarans when the sea is up.
The classic budget car ferry — the lowest fares of the three, sailing Donsak ↔ Lipa Noi (Samui) and also Donsak ↔ Koh Phangan, with sailings into the evening. The boats are older and a touch slower, and peak crossings get crowded — that's the trade for the lightest ticket price.
The old-school option that still runs on and off: a cargo-and-passenger boat leaving Surat Thani town pier late at night and reaching Nathon before dawn (~6 hours), sleeping on shared mattresses below a long deck. A few hundred baht and pure 1990s-backpacker atmosphere — check with agents in town that the sailing is currently running before you plan around it.
Travellers have been riding this route for decades and the system mostly runs itself, but four things are worth knowing before you go.
On ordinary days outside peak season you can buy at the pier or station counters with no drama. But around New Year, Songkran and the days either side of each Full Moon Party (when crowds surge through Samui toward Koh Phangan), sleeper berths and the best boat departures genuinely sell out — book online or through an agent several days ahead.
Samui's rain runs opposite to Phuket's — its wet season is late in the year, heaviest in November. On stormy days the fast boats cancel first; the big ferries handle waves better but can still be delayed. If you have an international flight to catch, keep a one-day buffer. From January–April and June–August the sea is usually far calmer.
The piers sit on the west coast (Nathon / Lipa Noi) while the famous beaches face east — Chaweng and Lamai are another 45 minutes–1 hour by road. Shared minibuses charging per person wait at the pier; taxis don't use meters, so agree the fare before you get in.
Prone to seasickness? Take a tablet 30–60 minutes before boarding, sit midship or on the breezy open deck, and watch the horizon — the big ferries ride steadier than the catamarans. On overnight coaches, keep passport, cash and phone on your body, never in the big bag.