Short answer: early October is usually fine with a flexible plan. Late October is a gamble. November is the wettest month of the year on Koh Samui and the Thai Department of National Parks sometimes closes Mu Ko Ang Thong entirely for days at a time. Here is what you actually need to know before you book, and what to do if the weather turns on your tour day.
Koh Samui's rainy season is opposite to Phuket's
This is the single most confusing fact for travelers. Phuket's monsoon peaks April�October on the Andaman side. Koh Samui's monsoon peaks October�December on the Gulf of Thailand side. So if you are choosing between Phuket and Samui in October or November, and weather is your priority, Phuket is drying out while Samui is getting wet. Our honest recommendation: pick Phuket for a late-October or November beach trip unless you have non-weather reasons to be on Samui.
Month-by-month on Samui � the raw truth
- October 1�15: Transitioning. 40�50% chance of rain on any given day. Ang Thong usually runs. Keep a flexible rebook window.
- October 16�31: Rain probability climbs to 50�70%. Swell starts. Tours still run most days but cancellations become normal.
- November 1�30: The wettest month. The park has historically closed for several days at a time. Expect cancellations. If Ang Thong is the only reason for your trip, reschedule or pick a different month.
- December 1�15: Rainy-to-dry transition. First two weeks risky, last two usually calm.
- December 16�31: Back to calm, peak season begins.
Will the park actually close?
Yes � it can. The Thailand Department of National Parks has the authority to close Mu Ko Ang Thong for visitor safety when waves exceed operating thresholds or when enforcement officers identify risk. In recent years, closure windows during November have ranged from 3 to 10+ days. Always check the latest notice at portal.dnp.go.th or ask a local booking team (we track it daily for our guests).
Refund policy if weather cancels your tour
Industry standard with legitimate operators:
- Operator cancels due to weather or sea conditions: 100% refund or free reschedule.
- Park officially closed: 100% refund or free reschedule.
- You cancel but the tour is running: penalties apply � usually 50% within 48 hours, 100% within 24 hours.
Always book through a verified operator who states this policy clearly. Always carry travel insurance that covers trip interruption. Cheap cash-only beach-tout tours may not offer refunds at all.
Should I even go to Koh Samui in October or November?
Yes � if you have other reasons beyond Ang Thong: honeymoon at a great resort, wellness retreat, diving from Koh Tao (with appropriate flexibility), Muay Thai training, cooking classes, or simply taking advantage of lower shoulder-season prices. No � if Ang Thong is the single reason for your trip. In that case rebook to January�April or May�September.
If you are coming anyway � build a "weather-flex" plan
- Book Ang Thong early in your trip so you have days to rebook if cancelled.
- Add 2 backup rainy-day activities: Big Buddha, cooking class, spa, Secret Buddha Garden.
- Buy travel insurance covering trip interruption.
- Use a booking team that monitors the park status daily and rebooks you free.
- Consider a big boat tour over speedboat � cancellation thresholds are more generous and the ride handles swell better.
When to rebook to if November is a wash
The easiest "plan B" months to rebook into:
- Last 10 days of December � reliable dry calm, festive season.
- January�April � best months for Samui, book early as high season fills fast.
- May�June � shoulder season, good value, occasional showers.
- September � usually calm before October turn.
Our honest final recommendation
If you already have a November Samui trip booked, do not panic � it just means planning two dry-weather activities and one flexible Ang Thong attempt. Book a big boat or small-group yacht (not a budget speedboat) so your cancellation and refund terms are stronger. Our Luxury Angthong Yacht Cruise [TK029] runs when safe and rebooks free when not.
Chat live ? tourinkohsamui.com � send us your dates and we will tell you honestly whether to book now, wait, or rebook. For the full 100-question Ang Thong guide, read The Honest Truth About Ang Thong Marine Park Tours (2026). Wondering if Ang Thong is worth it at all? Read the 4-minute answer.
Last updated: 22 April 2026. Tour In Koh Samui Local Team. Sources: Thailand Department of National Parks, Thai Meteorological Department, operator logs 2023�2026.
