The most useful thing to understand about Koh Samui is which coast of Thailand it is on. Samui sits in the Gulf of Thailand, on the eastern side of the peninsula. Phuket and Krabi sit on the Andaman side, in the west. The two coasts run on different weather cycles, and half the bad trip-planning advice about Thailand comes from treating them as one place.
When does it actually rain on Samui?
Samui's wettest stretch is broadly October to December. The Andaman coast's is roughly May to October. That means the months when Phuket's beaches are flying red flags are often perfectly good on Samui, and the months when Krabi is at its most beautiful are Samui's least reliable.
This is not a small detail. It is usually the difference between a good week and a wet one, and it is decided before you book.
The island itself
A single ring road circles Samui, so nowhere is hard to reach. What changes is tone.
Chaweng and Lamai
Chaweng is the long main beach: most of the nightlife, most of the development, most of the people. Lamai is the second-largest and a clear step calmer without being quiet.
Bophut and Maenam
Bophut on the north coast holds Fisherman's Village, a low-rise old-town strip that is the closest Samui gets to atmosphere rather than resort. Maenam, further west along the same coast, is quieter again and is where a lot of longer-stay visitors end up.
Phangan and Koh Tao are not the same trip
Samui is the transport hub for two islands that get lumped in with it and shouldn't be.
Koh Phangan is a ferry hop north. It is famous for the Full Moon Party, and that reputation obscures the fact that most of the island is green, quiet, and full of long-stay wellness and yoga people who are there specifically because it is not Samui.
Koh Tao is further north again and is a diving island. It is one of the cheapest places in the world to get certified, and that single fact shapes everything about who is there and what the island is for.
Getting there
Samui has its own airport, which is privately operated and priced accordingly. The alternative is the overland route: reach Surat Thani on the mainland by air or rail, then bus and ferry across. It costs a fraction of the flight and takes most of a day.
What changes on the ground
Ferry schedules shift with the season and the sea. Beaches that are lovely in March collect seaweed in other months. Which side of the island is sheltered depends on the week.
Browse Local Friends in Koh Samui on Roavi and ask someone who lives there, or start with the Koh Samui city guide.
Frequently Asked Questions
When is the rainy season in Koh Samui?
Roughly October to December, which catches people out. Samui is in the Gulf of Thailand on the east side of the peninsula, so it runs on a different weather cycle to Phuket and Krabi on the Andaman side. When the west coast is being hammered by the southwest monsoon in mid-year, Samui is often fine. The trade-off is that Samui's own wet spell lands at the end of the year, during what is peak season elsewhere in Thailand.Which Koh Samui beach should I stay on?
Chaweng is the long, busy main beach with most of the nightlife and the most development. Lamai is the second-largest and a step calmer. Bophut, on the north coast, has the old Fisherman's Village and a quieter, more low-rise feel. Maenam is quieter still. One ring road connects all of them, so the choice is about tone rather than access.How do Koh Phangan and Koh Tao relate to Samui?
They are separate islands, reachable by ferry from Samui in well under two hours. Koh Phangan is best known for the Full Moon Party but is otherwise much quieter and greener than that reputation suggests, with a large wellness and long-stay scene. Koh Tao is a diving island — it is one of the cheapest places in the world to certify — and is small enough to feel entirely different from either of the others.How do you get to Koh Samui?
Either fly into the island's own airport, which is privately operated and generally more expensive than other domestic routes, or take the cheaper overland option: fly or take a train to Surat Thani on the mainland, then a bus and ferry combination. The ferry route costs a fraction of the flight and takes most of a day.