Andaman vs Gulf: which Thai coast

The only comparison that matters first

January–March is when both can be good. October–November is when both can be annoying. That overlap is when people should lower expectations or stay inland.

Month fork (beach trip)

UK FCDO (retrieved 30 August 2026) still describes rain generally May–October, with Koh Samui and the south-east wetter November–March. That is the whole comparison.

Who should pick Andaman

• You want limestone, west-coast sunsets, and the classic “Thai island” photo in December–March.
• You will fly into Phuket and stay put or hop to Krabi/Lanta.
• You accept crowds and prices in high season.

Skip Andaman in September if boats and snorkelling are the point. Rain is not only rain: it is cancelled speedboats and red flags.

Who should pick the Gulf

• Your holiday is June–August.
• You care about Koh Phangan’s party calendar or Tao’s diving shops.
• You will tolerate Samui’s more developed south/east and hunt for quieter beaches.

November on Samui is a common “why is my honeymoon wet?” month. That is the northeast monsoon, not a random unlucky week.

Which island within the coast you picked

Choosing the coast is the decision that the calendar makes for you. Choosing the island is about what you want to do with the days.

On the Andaman side, Phuket is the one with the most flights, the most hospital capacity, and the widest range of prices, which makes it the low-friction choice even for people who dislike the idea of it. Krabi and Ao Nang trade nightlife for limestone scenery and easier access to day trips. Koh Lanta is flatter, quieter and more family-shaped. Koh Lipe is beautiful and far enough south that getting there is a real part of the trip.

On the Gulf side, Koh Samui has the airport, the resorts and the widest food range, at the cost of feeling developed on its north and east coasts. Koh Phangan is bigger and emptier than its party reputation suggests, but the Full Moon calendar dominates prices and boat traffic around those dates. Koh Tao is small and organised almost entirely around diving and freediving.

Rain is not the real problem — boats are

The reason the monsoon matters more here than in Bangkok is that island trips depend on sea conditions.

A wet afternoon on a beach is a minor inconvenience. A cancelled ferry, a red flag on the swimming beach, or a snorkelling trip called off at the pier can remove the actual reason you booked the trip. In the wetter window on either coast, that is the risk you are carrying, and it clusters into a few bad days rather than spreading evenly.

Two consequences follow. First, if you are travelling in a shoulder month, build a spare day into any island hop that has a flight at the end of it, because missing a boat should not mean missing a flight home. Second, prefer accommodation and tour operators with flexible cancellation in those months; the small premium is what you are actually buying.

Booking in the overlap months

October and November are where most of the bad decisions happen, because the coasts disagree and the prices look attractive.

If you can only travel then, the honest options are to lower the beach expectation and treat sunshine as a bonus, to keep bookings flexible and decide the coast a week out when forecasts mean something, or to spend more of the trip inland where the weather matters less to the itinerary. Committing to a non-refundable two-week Andaman beach holiday in early October is the version that disappoints people.

Common mistakes

• Choosing the island first and then discovering the coast is in its monsoon.
• Booking both coasts in seven days and spending two of them travelling.
• Assuming the Similan Islands are available year-round; they have a closed season.
• Reading a single rainy afternoon forecast as a ruined week, or a dry forecast as a guarantee.
• Planning a Full Moon trip without checking what that does to Phangan boat and room prices.
• Adding Chiang Mai to a beach itinerary because the map looks small.

Do not mix these up

• Patong is a nightlife strip on Phuket, not a synonym for Andaman.
• Koh Tao is a dive island in the Gulf, not “near Phuket.”
• Best time to visit Thailand is the country-wide version of this page. This page is the coast fork.

A 10-day first trip

Pick one coast. Add Bangkok nights at the front or back. Chiang Mai is a third climate (and haze) — see the north topic, do not glue it on because a map looks small.

If you want that trip written out rather than described, the 10-day Thailand itinerary is the worked version, and best time to visit Thailand covers the months at country level. If the north is in your plan for February to April, read burning season in Chiang Mai before booking those nights, because it is a real constraint rather than a footnote.

Ask in Islands and coasts with month and must-do (quiet vs party vs diving). People will tell you which island, not which brochure.