Khao Sok: A History Written in Stone and Forest
From ancient limestone formations to the creation of one of southern Thailand's most important protected landscapes.
THE LAND BEFORE THE FOREST
It began beneath an ancient sea.
Long before Khao Sok was covered in rainforest, this part of southern Thailand was shaped by an ancient marine environment. The limestone that now forms its cliffs and karst towers began as sediments on the floor of a shallow sea during the Permian Period, roughly 280–260 million years ago.
280–260 MILLION YEARS AGO
A shallow sea
During the Permian Period, this area lay beneath a shallow sea. Over time, carbonate-rich sediments accumulated and eventually formed thick layers of limestone. Fossils of marine organisms found in these rocks — including corals, brachiopods and crinoids — are evidence of that marine origin.
FROM SEABED TO LIMESTONE
The rock came first.
The limestone did not begin with the rainforest. It formed millions of years earlier, before geological forces lifted and fractured the rock. Those fractures later became important weak points where water could gradually reshape the landscape.
Khao Sok's Journey: Epidemics, Deforestation, and National Park DesignationFrom Crisis to Conservation, 1944–1980
THE LANDSCAPE TAKES SHAPE
Water did much of the sculpting.
Once exposed at the surface, fractured limestone was gradually dissolved and eroded by water. Over immense periods of time, this process helped create the steep cliffs, caves, valleys and isolated limestone towers that define Khao Sok today.
💡
Look at the Landscape
The limestone cliffs are more than a backdrop to Khao Sok. Caves, sheer rock faces and the tower-like formations around Cheow Lan Lake are different expressions of the same karst landscape — shaped by the underlying limestone and the long action of water.
HISTORY OF HUMAN MIGRATION AND SETTLEMENT IN KHAO SOK: FROM PREHISTORIC TIMES TO THE 18TH CENTURY
PEOPLE & THE LANDSCAPE
Before Khao Sok became protected.
Long before Khao Sok became a national park, people lived and worked around the forest. Communities developed along the valleys and waterways, while farming, roads and the use of forest resources gradually changed the relationship between people and the landscape.
LIVING WITH THE FOREST
The landscape was also a place to live.
For local communities, the Khao Sok area was more than wilderness. Valleys, rivers and forest edges provided places to settle, farm, travel and gather resources. Over time, small settlements became part of the wider landscape surrounding what is now Khao Sok National Park.
THE 20TH CENTURY
Access changed the relationship with the forest.
During the 20th century, improved road access connected this once-remote part of Surat Thani more closely with surrounding towns. Farming expanded in accessible areas, while logging and other forms of resource use placed increasing pressure on parts of the forest.
By the second half of the century, protecting the remaining forest had become increasingly important — setting the stage for Khao Sok's designation as a national park in 1980.
BEFORE THE NATIONAL PARK
A reconstruction of life around Khao Sok before national park protection.
Rivers and valleys provided natural routes through a landscape that was still difficult to access by road. Small settlements, farming and the use of forest resources gradually became part of the human story of the area.
Historical reconstruction of life around the Khao Sok landscape in the early 20th century.
A CHANGING FOREST
A reconstruction representing the growing pressure on the forest during the 20th century.
As access to the Khao Sok area improved, logging, agriculture and other forms of resource use expanded into more accessible parts of the landscape. These changes formed part of the wider conservation context that preceded Khao Sok's designation as a national park in 1980.
Historical reconstruction illustrating forest use and logging in the Khao Sok region during the 20th century.
A PROTECTED LANDSCAPE
Khao Sok becomes a national park.
1980
Khao Sok becomes a national park.
On 22 December 1980, Khao Sok was officially designated as Thailand's 22nd national park, protecting a large area of rainforest, limestone mountains and river systems in Surat Thani Province.
CHEOW LAN LAKE
Khao Sok National Park
HEADQUARTERS
🌳 FOREST
A large forest landscape
National park status brought a substantial area of Khao Sok's forest under formal protection and established conservation as a central purpose of the landscape.
🐾 WILDLIFE
Habitat under protection
Protecting the forest also protects habitat used by a wide range of native wildlife, from primates and hornbills to many smaller species that depend on intact forest.
⛰️ LANDSCAPE
More than rainforest
The protected landscape includes limestone mountains, caves, streams and river valleys as well as rainforest — the same natural systems that shape a visit to Khao Sok today.
738.74 KM²
KHAO SOK NATIONAL PARK TODAY
Khao Sok National Park covers approximately 738.74 square kilometres in Surat Thani Province and forms part of a much larger connected forest landscape in southern Thailand.
TWO YEARS LATER
Another transformation begins.
In 1982, construction began on a dam east of Khao Sok — a project that would eventually create the vast reservoir now known as Cheow Lan Lake.
1982–1987
A DAM TRANSFORMS THE LANDSCAPE
Another transformation begins.
Just two years after Khao Sok became a national park, another major change began to the east. Construction of what was then known as Cheow Lan Dam started in 1982, creating the reservoir that travellers know today as Cheow Lan Lake.
1982
Construction begins
Construction of Cheow Lan Dam began on 9 February 1982 as part of a major water-resource development project for southern Thailand. The project was designed for several purposes, including hydroelectric power generation, water management and irrigation.
1987
The reservoir takes shape
Construction was completed in September 1987. As water was impounded behind the dam, low-lying valleys were inundated and a new reservoir spread through the limestone landscape.
30 SEPTEMBER 1987
Rajjaprabha Dam officially opens
On 30 September 1987, the dam and hydroelectric power plant were officially inaugurated. The dam, originally known as Cheow Lan Dam, was given the name Rajjaprabha, meaning “Light of the Kingdom.”
THE LANDSCAPE CHANGES
Water creates a new geography.
Filling the reservoir changed the geography of the area. Valleys became waterways, higher ground became islands and limestone formations that once rose from a continuous land surface became surrounded by water.
185 KM²
RESERVOIR AREA
The reservoir covers approximately 185 square kilometres.
5,639 MILLION M³
STORAGE CAPACITY
The reservoir can store
approximately 5,639 million cubic metres
of water.
240 MW
GENERATING CAPACITY
The hydropower plant has an installed generating capacity of 240 megawatts.
💡
Look at the Landscape
The limestone cliffs are more than a backdrop to Khao Sok. Caves, sheer rock faces and the tower-like formations around Cheow Lan Lake are different expressions of the same karst landscape — shaped by the underlying limestone and the long action of water.
Ratchaprapha Dam
Originally known as Cheow Lan Dam, Rajjaprabha Dam was built by the Electricity Generating Authority of Thailand (EGAT) between 1982 and 1987. The 94-metre-high dam created the reservoir now widely known as Cheow Lan Lake, transforming the valleys behind it into the vast network of waterways and limestone islands seen today.
The dam remains in operation for hydroelectric power generation and water management, while the reservoir has since become one of the defining landscapes of the Khao Sok region.
FROM HISTORY TO THE PRESENT
A landscape still being protected.
The story of Khao Sok continues today.
The Khao Sok seen today has been shaped by changes across very different timescales — ancient geological processes, generations of human activity, the establishment of the national park and the creation of Cheow Lan Lake.
2021
ASEAN HERITAGE PARK
In 2021, Khao Sok National Park was recognised as Thailand's sixth ASEAN Heritage Park and the 50th in the regional network. The designation recognises protected areas of outstanding conservation importance across Southeast Asia.
WHAT REMAINS CONNECTED
Protection extends beyond one park.
Khao Sok forms part of a much larger protected landscape in southern Thailand. Together with neighbouring protected areas, including Khlong Saeng Wildlife Sanctuary, its forests provide connected habitat across an area far larger than the national park itself.
HISTORY CHANGES HOW YOU SEE KHAO SOK
The limestone cliffs are hundreds of millions of years old. Khao Sok National Park was established in 1980. Cheow Lan Lake took shape only a few years later.
Understanding those different timescales makes the landscape easier to read: ancient rock beneath the forest, a modern reservoir between the mountains, and a protected area whose story is still continuing today.