Mu Ko Ang Thong National Park is a group of 42 limestone islands about 20 km west of Koh Samui, and most people see it on a full-day boat trip from Samui. You climb to a viewpoint on Koh Wua Ta Lap, look down on the Emerald Lake on Koh Mae Ko, and kayak or snorkel in between. The main sites close every year from 1 November to 15 December.
Ang Thong was declared a national park on 12 November 1980, the second marine national park in Thailand, according to the government tourism agency DASTA. The Department of National Parks (DNP) describes it as roughly 84 km² of sea and 18 km² of island land. There are no towns or resorts in the park, so a day trip is the normal way to visit.
This page is about the day trip itself: what you will actually do, which boat to choose, the fee and the season. Our Koh Samui island guide covers the rest of the island and where to stay.
Ang Thong National Marine Park in brief
- Location
- About 20 km west of Koh Samui, Surat Thani province
- Islands
- 42, mostly limestone; park headquarters on Koh Wua Ta Lap
- Park fee
- 300 baht adult, 150 baht child for foreign visitors landing on Koh Wua Ta Lap and Koh Mae Ko (special zone; usually included in tour prices, October 2026)
- Annual closure
- 1 November to 15 December for the main beaches, the Emerald Lake, park bungalows and the campsite (DNP)
- Main sights
- Viewpoint on Koh Wua Ta Lap, Thale Nai (Emerald Lake) on Koh Mae Ko, Koh Sam Sao rock arch
- Time needed
- A full day, roughly 08:00 to late afternoon including transfers
The viewpoint climb on Koh Wua Ta Lap
Koh Wua Ta Lap ("sleeping cow island") is where the park headquarters sits, behind a white sand beach. DASTA's description of the park puts the trail to the summit viewpoint at about 400 meters. It is short but steep, with steps and uneven rock on the way up. From the top you see the whole chain of islands spread out across the water, which is the photograph most people come for.
Four hundred meters sounds easy, and on a cool morning it is. At midday in April it is hard work. Wear shoes that grip (not flip-flops), take water, and turn back if the rock is wet. Near the headquarters there is also Bua Bok cave, named after formations that look like lotus flowers.
Most tours give you a fixed window on Wua Ta Lap. If the viewpoint matters to you, ask the operator how long you get on the island before you book, because some itineraries spend most of the stop on the beach.
Thale Nai, the Emerald Lake on Koh Mae Ko
Koh Mae Ko holds Thale Nai, the "inner sea", a saltwater lake inside the island. DASTA describes it as a collapsed limestone basin, an oval about 250 by 350 meters and 7 meters deep. The color is a milky green that changes with the light, hence the English name Emerald Lake.
The boat ride from park headquarters takes about 15 minutes, then a walk of about 400 meters with steps brings you to a platform above the lake. You look at the lake rather than swim in it. It is the easier of the two walks and the one that works for older travelers and children.
Ask whether your tour lands on both Wua Ta Lap and Mae Ko. These two islands are the special fee zone and the reason to go. Cheaper "Ang Thong" cruises sometimes only sail past the islands or stop for snorkeling, and you will not see the lake from the water.
Kayaking, snorkeling and what the water is really like
Kayaking is the best way to see the cliffs and small sea caves, and many tours include an hour with a two-person kayak. The water is calm on most dry-season mornings. Wear a hat and a shirt; there is no shade on the water.
Snorkeling is the part to keep your expectations modest about. In a 2024 press visit the DNP said that the reefs around Ang Thong suffered widespread coral bleaching during the 2023 marine heatwave, and that snorkeling and diving there are limited because the water tends to be quite cloudy. If clear water and fish are your priority, a snorkeling trip around Koh Tao and Koh Nang Yuan is the better choice. Go to Ang Thong for the landscape.
The park also puts out nets against Portuguese man o' war jellyfish at its swimming spots, according to the DNP. Swim inside the netted areas, and read our guide to box jellyfish and other stings in Thailand before a Gulf trip; the Gulf islands see box jellyfish from July to October.
Bigger wildlife does turn up. In January 2026 the DNP recorded two Bryde's whales east of Koh Hin Dap, inside the park, and dolphins have been seen in the area. Sightings are a matter of luck, and no operator can promise them.
Speedboat or big boat from Samui
Day trips leave from piers on Samui's north and west coasts, usually with a hotel pickup. Tours from Koh Phangan also exist. There are two broad types of trip.
| Type | Crossing time | Good for | Drawbacks |
|---|---|---|---|
| Large tour boat | Around 2 hours each way | Shade, toilets, lunch on board, a calmer ride in some swell | Less time on the islands, larger groups at each stop |
| Speedboat | Roughly half that or less | More stops and more time ashore | Bumpy and wet in any wind, little shade, harder on bad backs and in pregnancy |
DASTA's page lists a boat leaving Nathon at 08:30 and returning from the park at 15:00, about two hours each way, but it is not dated, so treat that as an outline rather than a timetable. The ferry company Lomprayah also advertises a daily speedboat trip with snorkeling and kayaking. Whichever you choose, check that the price includes the park fee, lunch, kayaks and transfers, and ask what happens if the trip is cancelled for weather.
Boats between the islands are not risk-free. The UK Foreign Office notes that passenger boats in Thailand have sunk or collided, usually because of overloading, poor maintenance or rough monsoon seas. Look for life jackets you can actually reach, and do not board an overloaded boat. Our guide to ferries and boat safety in Thailand has a fuller checklist.
The park fee and how it is collected
Ang Thong is a Category 2 park under the DNP's fee schedule in force since 7 June 2022, which means 200 baht for a foreign adult and 100 baht for a child in most of the park. Koh Wua Ta Lap and Koh Mae Ko are a separate special zone where foreign visitors pay 300 baht per adult and 150 baht per child (as of October 2026). Thai visitors pay far less, which is normal in Thai national parks.
Most tour prices include the fee, so you will not handle cash at the park. If a cheap tour says the fee is "extra", bring cash in baht. Keep the ticket until the end of the day.
When Ang Thong closes, and the best months to go
In its announcement for the 2024 season, confirmed by the government's Anti-Fake News Center with the DNP, the park closed Ao Kha beach, Koh Wua Ta Lap, the Sam Sao beach, Thale Nai and several other beaches, plus the bungalow zone and the Wua Ta Lap campsite, from 1 November to 15 December. The reasons given were visitor safety in the monsoon weather and giving nature a chance to recover. The same window has been used in other years, but the DNP announces it each season, so check before you book a November trip.
The closure lines up with Samui's weather. Thai Meteorological Department figures for 1991–2020 show November as Samui's wettest month, with October to December bringing about half the year's rain. February to August is usually the calmer period for boats. Our guide to the best time for the Gulf and Andaman islands explains why Samui's rainy season is the opposite of Phuket's.
Even in season, a day trip can be cancelled at short notice if the wind picks up. If Ang Thong is a must for you, schedule it early in your stay so there is a spare day.
Staying overnight in the park
The park has a small number of bungalows and tents near the headquarters on Koh Wua Ta Lap, and a camping area where you can pitch your own tent. DASTA lists park accommodation from 600 to 1,800 baht a night, but that figure is undated. There are no restaurants beyond basic park facilities, so bring food and water. Book through the DNP's national park booking system, and note that the bungalows close with the rest of the main sites from 1 November.
Combining Ang Thong with the rest of your trip
Ang Thong fits on any day of a Samui stay; it does not matter much which beach you are based on, because most tours collect from hotels. See our comparison of Samui's beaches if you are still choosing, and our guide to getting to Koh Samui for flights and ferries. Travelers going on to Koh Phangan and Koh Tao can follow our Gulf island-hopping route.
Pack sunscreen, a hat, water shoes for the rocky landing points, a dry bag for your phone and some cash. The heat on the viewpoint trail catches people out; our advice on heat and sun in Thailand applies here as much as anywhere.
Frequently asked questions
Can you swim in the Emerald Lake at Ang Thong?
Visitors view Thale Nai from a platform at the end of a stepped trail of about 400 meters; it is a protected saltwater lake inside Koh Mae Ko, not a swimming spot. You can swim at the beach on Koh Wua Ta Lap, inside the netted area the park sets up against jellyfish.
How much is the Ang Thong park fee?
For foreign visitors landing on Koh Wua Ta Lap and Koh Mae Ko, 300 baht per adult and 150 baht per child (October 2026). The rest of the park is Category 2 at 200 baht per adult. Most tours include the fee, so check the small print before you pay extra.
Is Ang Thong open in November?
Usually not. The DNP closes the main beaches, the Emerald Lake, the park bungalows and the campsite from 1 November to 15 December each season, during the northeast monsoon. Check the park's announcement for the current year before booking a trip in late October or December.
Is the Ang Thong viewpoint hike difficult?
It is short, about 400 meters, but steep and uneven underfoot. Reasonably fit people manage it in good shoes. It is not suitable in flip-flops, in the rain or for anyone with poor balance; the Emerald Lake walk on Koh Mae Ko is easier.
Is Ang Thong good for snorkeling?
Only moderately. The DNP reports that the water around the park is often cloudy and that the reefs bleached widely in 2023. Most people go for the scenery, the viewpoint and the kayaking. For clearer water, a snorkeling trip around Koh Tao is the better choice.
Sources
- DASTA (Designated Areas for Sustainable Tourism Administration) – Mu Ko Ang Thong National Park (checked October 2026)
- Department of National Parks – Press visit to Mu Ko Ang Thong and Hat Khanom national parks, July 2024 (checked October 2026)
- Department of National Parks – Bryde's whales sighted in Mu Ko Ang Thong National Park, January 2026 (checked October 2026)
- Department of National Parks – National park entry fees by group from 7 June 2022 (checked October 2026)
- Anti-Fake News Center Thailand – Closure of tourism and overnight stays in 11 national parks (verified with the DNP) (checked October 2026)
- UK Foreign Office – Thailand: safety and security (checked October 2026)
- Lomprayah – Ferry and day-trip operator, Koh Samui (checked October 2026)