May 15, 2026, was the last day of access to the Surin Islands before five months of closure. The Thai Department of National Parks (DNP) closes this archipelago in the Andaman Sea every year during the monsoon season, to allow the reefs to recover and to spare visitors from unstable seas.
If you are planning a diving trip to Thailand, this date weighs more than any reef photo. Our old page announced a season from November to April and “possible” access off-season. The park is closed during this period.
So we revised the article with a simple framework: level, current, season, supervision, and fallback plan. Two sites wrongly listed in the park have also been removed from the list.
When is Mu Ko Surin National Park open?
The park generally opens from mid-October to mid-May. In 2025, the DNP closed it from May 16 to October 14, according to the announcement published by the Thai government. For 2026, the Thai press reports a closure from May 16 to October 15. Check the exact reopening date before paying a deposit, because a one-week difference can turn a planned departure into waiting at the port.
Outside this window, no tourist trips enter the park.
The park can also close earlier than expected. Bad seas at the end of the season sometimes bring the date forward, and a cruise booked for the last week of May then runs a real risk of cancellation or itinerary change decided by the operator. Ask what happens in this case. You want a written answer. Refund or postponement, both are negotiable before departure.
But opening dates do not solve everything. Our old page also boasted “pleasant water all year round” and “exceptional” visibility, without date or source, so we remove these two claims. Clear water says nothing about the current.
Richelieu Rock: for what level and with what current?
Richelieu Rock is an isolated pinnacle that is part of Mu Ko Surin park, about twenty kilometers from the main islands. Its summit approaches the surface. Its base descends to about 30 to 35 meters, as an indication. The required level depends on the current of the day and the profile the guide chooses on site.
This horseshoe-shaped rock attracts divers for its reef fauna and pelagic fish. Whale sharks and manta rays pass by from time to time. Nothing guaranteed. Our old page spoke of “frequent encounters,” a promise that no dated source can support, and we remove it without regret. The site is included in our selection of best diving destinations in Thailand for its reputation, and this reputation does not guarantee any encounters.
The current decides more than the photo.
Yet, we have no public and dated current data for Richelieu Rock. Imagine an offshore pinnacle, unprotected, where the ascent would be in open water with a safety sausage because the boat cannot come close to the rock. For what level? The center will tell you according to the tide. Ask the expected depth, the time of entry into the water, and the procedure if you lose your group.
What remains of the reefs after the 2010 bleaching?
In 2010, a marine heatwave bleached the corals of the Andaman Sea. In Thailand, more than 80% of corals were affected on all monitored sites, according to the Reef Resilience Network. Authorities then closed eighteen diving sites in seven national parks, for six to eighteen months.
At Surin, the closure announced by the DNP on January 21, 2011, targeted Ao Suthep, Ao Mai Ngam, and Ko Stork, according to the Thai press at the time. Diving and snorkeling were suspended there. The 2011 assessment remained bleak. On average, less than 5% of damaged corals had recovered that year on the reefs monitored in Thailand, which led to extending some closures. The precise condition of each site in 2026 is unknown.
Yet it is the reef of today that you will see, and no one can describe it to you from here with certainty.
In 2019, park officials estimated in the local press that about 90% of the damaged corals had regenerated, while a new bleaching episode had just been reported in May of the same year. Impossible to decide from here. Our article on the threats facing corals explains the mechanism. On site, keep your fins away from the bottom. The reasons why you should never touch marine life apply doubly on a reef that is rebuilding.
How much does the entrance fee cost and how does the exit work?
The entrance fee displayed for foreign visitors is 500 baht per adult and 250 baht per child aged 3 to 14, according to the park’s public fact sheets updated in 2026. This rate may change from season to season. Ask your operator if it is included in the price.
Two formats exist. The day trip departs by speedboat from the coast of Phang Nga, and the multi-day cruise often combines Surin, Richelieu Rock, and the Similan Islands. The journey matters. A long crossing early in the morning, on a rough sea, tires you before the first dive and reduces your margin if conditions worsen underwater. The park has offered tents and bungalows on the islands, but check their availability for your season.
Thus, by choosing the format, you also choose your travel time, your wake-up time, and the fatigue you carry into the water.
A Moken community, sea nomads, lives on the island of Ko Surin Tai. If you pass through their village, ask before photographing anyone. Dress appropriately. Our old page promised craft workshops and canoe outings that we could not verify, so we have removed them.
What backup plan should you consider around the Surin Islands?
Your backup plan depends on the reason for cancellation. If the sea closes Richelieu Rock one day, the operator can offer you a more sheltered reef around the islands. If the entire park is closed, you need to change dates. Koh Bon and Koh Tachai won’t help you: they belong to the Similan National Park, closed on the same dates.
Our previous version listed them among the Surin sites, and that was a mistake.
| Criterion | Richelieu Rock (scuba) | Reefs around the islands (snorkeling) |
|---|---|---|
| Level | Set by the center according to the depth and current of the day | Comfortable with fins, mask, and snorkel, vest if needed |
| Current | No dated public data, to be asked the day before | No dated public data |
| Season | Park open from mid-October to mid-May (DNP, 2025) | Same dates |
| Supervision | Center guide, group size to be confirmed | Guide on the boat, ratio to be confirmed |
| Backup plan | A more sheltered site in the park | Another bay or another day |
However, days without diving are not lost. The shallow reefs around the islands are suitable for snorkeling, and the guide decides if entering the water remains reasonable. Further north, the Mergui Archipelago, on the Myanmar side, receives cruises departing from Thailand, with other formalities and conditions that we cannot date from here. Our page on diving in the Mergui Islands details them. Check the country’s situation before booking.
In short, a cruise scheduled for the last days of opening makes you pay a premium, with a park that can close earlier than expected and a sea that the monsoon makes less stable. Aiming for the middle of the season gives you buffer days for often a higher price. Would you book it that way?
FAQ
Are the Surin Islands open in October?
Only after the annual reopening, around mid-October. In 2025, the park reopened on October 15. For 2026, the announced closure runs until October 15, so check the DNP announcement before booking the second half of the month.
How much does the Mu Ko Surin National Park entrance fee cost?
The park’s public fact sheets indicate 500 baht per foreign adult and 250 baht per child aged 3 to 14. This rate may change. Ask your operator if it is included in the trip price.
Is Richelieu Rock suitable for a beginner diver?
No one can say from a distance. The site is an offshore pinnacle, with no public and dated current data. The center decides based on your certification, recent experience, and the day’s conditions.
Is Koh Tachai part of the Surin Islands?
No. Koh Tachai and Koh Bon belong to the Mu Ko Similan National Park. They close during the monsoon at the same dates as Surin.
Sources
- Similan Islands and Surin Islands to be temporarily closed from 16 May to 14 Oct 2025 (Thailand Government Public Relations Department, based on DNP, 2025)
- Malaysia & Thailand: Disturbance Response (Reef Resilience Network, The Nature Conservancy, accessed in 2026)
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