Phuket Boat Trips in the Green Season (May to October): What Changes

Yes, you can take a private boat trip from Phuket between May and October. What changes is certainty. This is the southwest monsoon season, when the sea can turn rough for days at a time, some national park areas close, and the captain's weather call matters more than at any other time of year.

This guide explains what the official sources say about the season, what a Thai Meteorological Department (TMD) warning means for a small boat, which closures fall in this period, and what to agree with the operator before you pay a deposit.

When the green season is, according to the official sources

Thailand's government guide to the seasons, published on thailand.go.th, puts the rainy season between mid-May and mid-October. It says the season starts when the southwest monsoon covers Thailand, and that the start can come one to two weeks earlier or later than expected. So "May to October" is a guide, not a switch that flips on a set date.

Operators often call this period the green season. The charter FAQ from Blue Andaman, the charter service behind this site, uses that name for roughly May to October and describes it as quieter and lusher.

For a boat trip, the state of the sea matters as much as the rain, and the official reference for sea conditions is the TMD.

What TMD sea warnings say, and what they mean for small boats

During the monsoon, the TMD issues weather advisories that cover wave heights in the Andaman Sea. Two examples from 2026 show how they read:

• 28 May 2026 (No. 3, 81/2026). The TMD forecast waves of 2 to 3 metres in the upper Andaman Sea, which it defines as from Phuket northward, and above 3 metres in thundershowers. Its advice: all ships should proceed with caution and keep off thundershowers, and "small boats in the upper Andaman Sea keep ashore".
• 13 July 2026 (No. 10, 126/2026). The TMD linked the conditions to a strong southwest monsoon and forecast waves of 2 to 4 metres in the upper Andaman Sea, above 4 metres in thundershowers. It again said small boats should keep ashore, and gave 13 to 15 July as the period of strong winds and high waves.

The wording is plain: when the TMD says small boats should keep ashore, it is telling small boats not to go out. The advisories do not define which boat sizes count as "small", so do not try to work out for yourself whether your boat qualifies. Ask the operator how they apply TMD advisories, and expect a cancelled or postponed trip on days like these.

The advisories are also short-term. Each one names a period of effect and when the next update is due, so a warning a few days before your trip does not mean your date is lost. It is a reason to keep in touch with the operator and stay flexible.

Park closures that fall in this period

Two well-known destinations are off the list for part of the green season.

Mu Ko Similan National Park. In 2026, the Similan Islands and the Surin Islands closed to tourists for five months by order of the Department of National Parks, Wildlife and Plant Conservation. Thairath reported that 15 May was the last day to visit and that the closure ran until 15 October; The Nation reported the same mid-May to mid-October window. Both reports give two reasons: letting the ecosystem recover and avoiding the dangers of unstable monsoon weather. If the Similans are the main reason for your trip, plan for the October to May season and check the park's announcement for your year, because dates are set annually.

Maya Bay. Maya Bay on Phi Phi Leh closes every August and September, according to Time Out Bangkok, which reported that it reopened on 1 October 2026. Even when the bay is open, swimming there is not allowed under the park's conservation rules. A trip in August or September can still pass Phi Phi, but not stop at Maya Bay.

Closures are not limited to the dates above. Time Out Bangkok advises checking the national park's latest notice and your operator's itinerary, and the same applies to any park on your route.

Routes: let the captain choose on the day

In the green season the route you book may not be the route you sail. The private day charter page of the charter service behind this site says the captain may adjust stops for weather, sea conditions and access restrictions, and that added destinations or longer hours need agreement and may affect the cost. Its FAQ adds that the crew watch conditions and will recommend sheltered itineraries when the weather calls for it.

You may read that one bay or another is "always calm" in the monsoon. No official source saying so for any specific area was available when this guide was checked, so it is not promised here. Even the Phang Nga Bay charter guide simply notes that conditions and park access vary through the year, and asks you to check the route and stops for your date. The practical approach is to ask the captain, a day or two before, which route they recommend for the forecast, and to treat your wish list as a preference rather than a fixed plan.

A few habits help:

• Keep crossings short. A long open-water crossing is the part of the day most exposed to swell. A nearer route leaves more room for a change of plan.
• Choose the boat for the conditions. Our guide to choosing between a catamaran and a speedboat explains how the ride differs in choppy water.
• Leave spare days. If your trip falls early in your holiday, a postponement can still fit into your stay.

Weather calls and rescheduling: what to ask

In the green season, clear terms matter as much as the forecast. Before you pay a deposit, find out who makes the call, when, and what happens to your money.

The FAQ of the charter service behind this site says that if the captain deems it unsafe to sail, it will work with you to reschedule or find a fair solution. It also says deposit amounts and cancellation windows vary by yacht and season, and are set out in your quote and confirmation. That is a reasonable starting point, but the details are what count, so get them in writing for your booking.

The same applies to any operator. Our guide on how to choose a yacht charter company in Phuket covers the wider checks worth making before you commit.

On price: rates and deposit terms vary by yacht and season, so ask for a quote for your exact dates rather than assuming the green season is cheaper.

Questions to ask before you book

• Who decides whether the trip goes ahead, and by what time will we know?
• How do you apply Thai Meteorological Department advisories, such as a "small boats keep ashore" warning, to this boat?
• If the captain cancels for weather, can we reschedule, and what happens to the deposit if no other date works?
• If we choose to cancel because of the forecast, but you would still sail, what are the terms?
• Which route would you suggest for our dates, and what is the alternative if the sea is rough?
• Are any parks on our planned route closed on our dates (for example the Similan Islands or Maya Bay)?
• Does a change of route on the day change the price?
• Is there covered space on board for everyone if it rains?
• Are there life jackets on board in the right sizes for every guest, including children?