- Ang Thong guide
- Emerald Lake
Emerald Lake Thale Nai on Koh Mae Ko
A green saltwater lake hidden inside the limestone walls of Koh Mae Ko, joined to the sea only through underground tunnels. You see it from a viewing platform at the top of a stairway, and every tour to Ang Thong stops here.
- Viewpoint
- Stairway with handrails
- No swimming
- On every tour
Emerald Lake at a glance
Checked:
- Local name
- Thale Nai ("inner sea"), also written Talay Nai
- Where
- Koh Mae Ko ("mother island"), in the north of Mu Ko Ang Thong National Marine Park, about 28 km west of Koh Samui
- Water
- Salt water, connected to the sea through underground tunnels; the level rises and falls with the tide
- Access
- Stairway with handrails from the beach to a viewing platform above the lake; short but steep in places
- Swimming
- Not allowed, to protect the lake
- Entrance
- Covered by the national park fee: ฿300 per adult, ฿150 per child
- Tours
- Speedboat, VIP speedboat, big boat, Red Baron and private charters all stop at Mae Ko
A lake inside an island
Mae Ko looks like an ordinary green island from the boat. Its limestone walls, though, form a ring around a hollow in the middle, and inside the ring lies Thale Nai, the Emerald Lake: a lagoon of milky green salt water enclosed on every side by cliffs and jungle.
The lake is connected to the open sea only through tunnels in the rock, below the water line. That is why its level rises and falls with the tide, yet you never see where the sea comes in. The colour changes with the light and the season, from jade to turquoise.
A local legend says the lake sits in the mouth of a sleeping volcano. Geologically it is limestone, but the story fits the place: from the platform the lake looks like a crater filled with green water.
The stairway to the viewpoint
From the beach on Mae Ko a stairway with handrails climbs through the rocks and the forest to a wooden viewing platform above the lake. The climb is short, but some steps are steep and high, and in the midday sun it is hot work: take water and wear shoes with grip rather than flip-flops.
At the top there is room for a group on the platform, with the lake directly below and the cliffs around it. Most people spend a few minutes taking photos and then walk down the same way.
Swimming in the Emerald Lake is not allowed. The lake is a closed ecosystem and the park keeps people out of the water to protect it; you enjoy it from above.
Which tours stop at the lake
There is no public ferry to Ang Thong, so you see the Emerald Lake on a day tour from Koh Samui. Every tour includes it, at a different time of day:
- Speedboat tourMae Ko at about 11:00, after the morning snorkeling stop. Daily, ฿1890 per adult.
- VIP speedboat tourMae Ko is the first stop, at about 09:15. Tue, Thu, Sat; park fee included.
- Big boat tourMae Ko in the afternoon, around 13:30. With the kayak option you paddle to the island; without it a longtail boat takes you ashore.
- Red Baron sailing cruiseMae Ko at about 10:30, with time for the viewpoint and the lake before lunch on board. Wed and Sat.
- Private speedboatThe route is yours: most guests include the Emerald Lake with Wua Ta Lap and Koh Phaluai.
Emerald Lake in pictures
Tours that go there
All tours include hotel pickup on Koh Samui. Book online, no payment now.
- Days
- Daily
- Time
- 07:40-16:30
- Boat
- Shared speedboat
- Park fee
- ฿300 extra
- Days
- Tue, Thu, Sat
- Time
- 07:00-17:30
- Boat
- Small group, max 16
- Park fee
- Included
- Days
- Daily
- Time
- 07:30-17:00
- Boat
- Large tourist boat
- Park fee
- ฿300 extra
- Days
- Wed, Sat
- Time
- 07:30-19:00
- Boat
- Traditional sailing junk
- Park fee
- Included
Emerald Lake: questions and answers
Can you swim in the Emerald Lake in Ang Thong?
No. Swimming in Thale Nai on Koh Mae Ko is not allowed, to protect the lake. You see it from the viewing platform at the top of the stairway.
How do I get to the Emerald Lake from Koh Samui?
Only on a tour or a private boat: there is no public ferry to Ang Thong. Every day tour from Koh Samui stops at Mae Ko, including the speedboat (about 40 minutes each way), the VIP speedboat, the big boat (about 1.5 hours) and the Red Baron.
Is the climb to the Emerald Lake difficult?
It is short but steep in places, on a stairway with handrails. Most people manage it at their own pace; take water and wear shoes with grip.
Is the Emerald Lake salt water?
Yes. It is connected to the sea through underground tunnels in the limestone, so the water is salty and the level changes with the tide.
Do I need to pay to see the Emerald Lake?
The lake is inside the national park, so the park fee applies: ฿300 per adult and ฿150 per child. It is already included in the VIP speedboat and Red Baron prices.
