Ton Sak Yai National Park

A Tree That Remembers the Forest

Known as Mahesak, this enormous teak stands within Ton Sak Yai National Park in Nam Pat District, Uttaradit.

Estimated at around 1,500 years old, Mahesak is recognised by Thai government sources as the world’s largest living teak tree.

But the tree is only the beginning. Beyond Mahesak lies mixed deciduous forest, dry evergreen forest, mountain streams, waterfalls, caves and high peaks — including Phu Miang at approximately 1,656 metres.

Ancient forest, mountain water and one extraordinary living tree — together.

At a Glance

~1,500 years

Estimated age of Mahesak, the giant teak.

518.80 km²

Official park area — 324,240.80 rai.

1,656 m

Phu Miang — the park’s high mountain.

Park No. 103

Established 4 December 2003.

2012

Renamed from Khlong Tron National Park.

Official Name

Ton Sak Yai National Park

Thai Name

อุทยานแห่งชาติต้นสักใหญ่

Province

Uttaradit

Main Districts

Nam Pat, Mueang Uttaradit, Tha Pla and Thong Saen Khan

Former Name

Khlong Tron National Park

National Park No.

103

Established

4 December 2003

Renamed

12 July 2012

Official Area

324,240.80 rai / 518.80 km²

Highest Mountain Area

Phu Miang — approximately 1,656 m

Signature Landmark

Mahesak, the giant teak tree

Landscape

Mixed deciduous, dry evergreen, hill evergreen and pine forest

Famous For

Mahesak, Khlong Tron, Huai Khom, Huai Sai, caves and Phu Miang

Best For

Nature, photography, hiking, waterfalls, camping and forest exploration

The Department of National Parks lists Ton Sak Yai at approximately 324,240.80 rai (518.80 km²), covering forest across several districts of Uttaradit.

Why Ton Sak Yai Is Special

Many national parks are known for a mountain. Others for a waterfall. Ton Sak Yai has something much older.

A living tree.

Mahesak has survived for an estimated 1,500 years — a reminder of the vast teak forests that once covered large parts of northern Thailand. The park preserves the broader ecosystem around it: mixed deciduous and dry evergreen forests, mountain streams and highland habitats.

The tree is the symbol of a living forest — not an isolated monument.

The Story of Mahesak

Thailand’s giant living teak

The tree known as Mahesak was reportedly discovered around 1927, then protected as the centrepiece of the Ton Sak Yai Forest Park from 1968.

Historical measurements recorded on 18 June 2000:

47.8 m

Height measured in 2000.

10.07 m

Trunk circumference measured in 2000.

~10.22 m

More recent provincial circumference figure.

Thai government sources commonly describe Mahesak as the largest living teak tree in the world.

The Name Mahesak

On 29 September 2009, the giant teak was named “Mahesak” by Her Royal Highness Princess Maha Chakri Sirindhorn.

Earlier, on 14 January 1998, Her Majesty Queen Sirikit visited the tree and gave guidance that it should be carefully maintained for as long as possible. Forestry and national-park authorities then established a conservation committee.

The park continues to protect Mahesak through careful soil management and controlled visitor movement around its base.

Protecting the Giant Tree

Visitors do not walk directly on the soil at the tree’s base. A raised wooden walkway lets you see Mahesak at close range while reducing compaction of the root zone.

Look closely. Let the tree remain untouched.

The Mahesak Forest Park Area

The area around the giant teak was historically managed as Ton Sak Yai Forest Park. Today it is the most accessible visitor experience in the national park.

• The giant Mahesak teak
• Raised viewing walkway
• Small exhibition area
• Interpretation about the tree
• Forest scenery
• Nature-study trail (~2 km)
• Visitor facilities

The trail is an easy way to explore mixed forest beyond the tree itself — shifting the visit from “see the big tree” to “understand the forest that protects it.”

From Khlong Tron to Ton Sak Yai

The park’s changing identity

The protected area was originally established as Khlong Tron National Park, named for a major stream system in the forest. Surveyed from the late 1980s into the early 1990s, it became Thailand’s 103rd national park on 4 December 2003.

On 12 July 2012 it was renamed Ton Sak Yai National Park, reflecting the outstanding significance of the giant teak.

Khlong Tron

The mountain watershed.

Ton Sak Yai

The ancient teak forest.

The Khlong Tron Watershed

Mountains collect rainfall and feed streams that eventually flow toward the Nan River. Khlong Tron is a major watercourse formed by smaller forest streams — supporting wildlife, vegetation and communities downstream, and creating the park’s signature waterfalls.

Mountain → Forest → Stream → Waterfall → Nan River

The Mountains of Ton Sak Yai

Ton Sak Yai is a mountainous landscape. Important features include Phu Miang, Khao Khwam Ruea, Khao Ngang Ruea, Khao Sam Liam, Khao Yuak, Khao Thanon, Khao Daet, Khao Mai Pha, Khao Tak Bon, Khao Nam Yoi, Khao Phak Khuang and Khao Chan.

The highest area is Phu Miang at approximately 1,656 m, along the mountainous rim between Uttaradit and Phitsanulok.

Phu Miang

The high mountain of Ton Sak Yai

At about 1,656 metres, Phu Miang is dramatically different from the Mahesak visitor area. Large cliffs, mountain viewpoints and, in clear weather, views across Uttaradit and Phitsanulok toward Sirikit Dam.

The route passes through changing forest — rhododendrons, ferns, wild mountain plants, orchids and other highland species — and a sequence of waterfalls.

This is a serious trekking experience, not a casual nature walk.

The Phu Miang Trek

The summit area has limited facilities. Camping may be possible under designated conditions — carry what you need. The environment grows cooler and more exposed toward the ridge.

• Long walking distances
• Steep, uneven forest trails
• Wet conditions
• Limited facilities
• Changing temperatures
• Overnight camping readiness
• Remote surroundings

Khlong Tron Waterfall

A forest waterfall in two sections

Khlong Tron Waterfall is formed by Huai Khlong Tron. The first section has about four tiers (~20 m combined). A second fall farther along reaches about 30 m.

Access is on foot — different from the easy Mahesak area. That contrast is part of the park’s character.

Huai Khom Waterfall

Near Ban Huai Khom, this is a sequence of three falls: roughly 15 m, then two tiers totalling ~15 m about 200 m upstream, then a ~20 m single drop farther on.

About 5 km from Ban Huai Khom — vehicles cannot reach the falls. A remote forest experience, not a roadside stop.

Huai Sai Waterfall

A single-drop fall of about 35 metres on Huai Sai, associated with the Khao Khwam Ruea area. Quieter forest setting; volume changes with rainfall. Follow local safety instructions before approaching the water.

Huai Niam & Other Waterfalls

Official park information also identifies Huai Niam and Mon Kaew among the park’s stream attractions. Accessibility varies; some routes need forest walking.

Present them as nature attractions within a large protected landscape — not as same-day stops from one entrance.

Caves of Ton Sak Yai

• Tham Chan
• Tham Chedi
• Tham Suea Dao
• Tham Pha Tang

Forest Ecosystems

Mixed deciduous

Teak, afzelia, padauk, lagerstroemia and related species — brighter and more open in the dry season as leaves fall.

Dry evergreen

Hopea, dipterocarps, yang, wild mango and denser year-round canopy where moisture is higher.

Hill evergreen

Cooler, wetter montane plants, ferns and mosses around Phu Miang and higher ridges.

Pine forest

Higher-elevation pine communities in the park’s official vegetation record.

Wildlife & Birdlife

Species documented in official descriptions include serow, bear, sambar, muntjac, mouse deer, wild boar, clouded leopard, fishing cat, civets, slow loris, porcupine, squirrels, barking deer, reptiles and numerous birds.

Serow and clouded leopard signal the ecological importance of remote mountain forest. Sightings are unpredictable — wildlife is often present without being visible.

For birds: songbirds, woodpeckers, drongos, bulbuls, pigeons, raptors and water-associated species. Move slowly. Bring binoculars if observation is a priority.

Seasons & When to Visit

October – February · Cool ★★★★★

Higher mountains cool down. Comfortable for hiking and forest exploration; pleasant mornings.

March – April · Hot

Lower elevations heat up; deciduous forest opens as leaves fall. Start early and carry water on longer walks.

May – September · Rainy

Stronger waterfalls and deep green forest. Trails can be slippery; access to falls and mountain routes may change.

For Mahesak

Visitable year-round, subject to current park conditions.

For waterfalls

Rainy season generally offers stronger flow.

For hiking

Cooler months are more comfortable; trail access follows the park schedule.

For Phu Miang

Trekking season is controlled and may close annually — check with the park.

Ton Sak Yai for Hikers

Easy · Mahesak

Giant teak → forest trail → visitor area. Suitable without a major trek.

Adventure · Phu Miang

Mountain trail → waterfalls → high forest → summit. For experienced hikers only.

Two sides of the same protected landscape — never present them as equivalent.

Camping

Zone 1

Park Headquarters — accommodation, tents and camping area.

Zone 2

Ton Khon Nun Ranger Station — about 45 km from headquarters; accommodation and camping.

How to Get There

Ton Sak Yai National Park is in Nam Pat District, Uttaradit.

From Phitsanulok

Phitsanulok–Uttaradit route, then Highway 1047 toward the park — about 53 km on 1047 from the relevant junction.

From Uttaradit / Sirikit Dam

Uttaradit–Sirikit Dam–Nam Pat route, then Highway 1047 — about 9 km on 1047 from the junction.

Confirm navigation locally before travelling into remote areas.

Visiting Mahesak

A visit does not require a strenuous hike. Allow time to:

1

Walk to the giant teak.

2

Follow the raised walkway.

3

Read the interpretation panels.

4

Visit the exhibition area.

5

Walk the nature-study trail.

6

Explore the surrounding forest.

The experience deepens when the tree is seen in its ecological context — a survivor of an ancient forest landscape, not a botanical-garden specimen.

Responsible Travel

Mahesak is a living organism. Help protect it.

• Do not touch the trunk unnecessarily
• Do not climb the tree
• Do not step off the raised walkway
• Do not damage roots or soil
• Do not carve names into the bark
• Do not collect leaves, seeds or branches
• Do not leave rubbish

In the wider mountain forest:

• Stay on designated routes
• Do not feed or approach wildlife
• Do not collect plants
• Do not enter caves without permission
• Do not leave food waste or use soap in streams
• Carry your rubbish out

The less evidence visitors leave behind, the better.

Uttaradit’s Forest Heritage

Uttaradit has a long relationship with teak. Mahesak has become one of the province’s natural symbols — and the story is no longer about extracting teak. It is about understanding what remains: conservation, heritage and ecological value.

Why Visit Ton Sak Yai?

Few travel experiences let you stand beside a tree that has survived roughly fifteen centuries. The park also offers ancient teak forest, mountains, waterfalls, caves, highland vegetation, wildlife, remote hiking and mountain viewpoints.

• Ancient teak
• Mountain forests
• Waterfalls
• Caves
• Highland vegetation
• Wildlife
• Remote hiking
• Forest streams
• Mountain viewpoints

ThailandLover Travel Guide

Best for

Nature lovers · Photographers · Forest explorers · Hikers · Campers · Wildlife enthusiasts

Travel style

Nature + Heritage + Hiking + Wildlife

Don’t miss

Mahesak · Nature trail · Khlong Tron · Huai Khom · Huai Sai · Phu Miang

Best experience

Start with Mahesak, then the surrounding forest — plan Phu Miang as a separate mountain trek.

Travel character

Ancient · Wild · Quiet · Forested · Remote

Essential Information

Park

Ton Sak Yai National Park · อุทยานแห่งชาติต้นสักใหญ่

Location

Nam Pat District, Uttaradit, Thailand

Former name

Khlong Tron National Park

Established

4 December 2003 · National Park No. 103

Renamed

12 July 2012

Official area

324,240.80 rai / 518.80 km²

Signature landmark

Mahesak — ancient giant teak (~1,500 years)

Historical measurement

47.8 m height and 10.07 m circumference (18 June 2000)

Recent circumference

Approximately 10.22 m (provincial figure)

High mountain

Phu Miang — approximately 1,656 m

Main waterfalls

Khlong Tron · Huai Khom · Huai Sai · Huai Niam · Mon Kaew

Caves

Tham Chan · Tham Chedi · Tham Suea Dao · Tham Pha Tang

Forest types

Mixed deciduous · Dry evergreen · Hill evergreen · Pine

Main visitor area

Mahesak / Ton Sak Yai Forest Park area

Nature trail

Approximately 2 km

Park contact

+66 89 958 6759

Frequently Asked Questions

What is Ton Sak Yai National Park?

A mountain forest park in Uttaradit, best known for Mahesak — an ancient living teak — plus Phu Miang, waterfalls, caves and mixed forest. Established 2003 as Khlong Tron; renamed Ton Sak Yai in 2012.

Where is it, and how large is it?

Nam Pat, Mueang Uttaradit, Tha Pla and Thong Saen Khan. About 324,240.80 rai, or 518.80 km².

What is Mahesak?

The park’s giant teak, named in 2009 by HRH Princess Maha Chakri Sirindhorn. Measured in 2000 at about 47.8 m height and 10.07 m circumference; later provincial circumference about 10.22 m.

When is the best time to visit?

Cool season for hiking; rainy season for stronger waterfalls; Mahesak year-round subject to park conditions. Confirm Phu Miang dates with the park.

Is Phu Miang hard?

Yes — a serious remote trek at about 1,656 m, not equivalent to the easy Mahesak area.

How do I get there?

Highway 1047 from the Phitsanulok–Uttaradit or Sirikit Dam–Nam Pat approaches. About 53 km or 9 km on 1047 depending on the junction.

Can I camp there?

Yes — Zone 1 at headquarters and Zone 2 at Ton Khon Nun Ranger Station. Check the DNP reservation system.

More Parks Near Uttaradit & the Nan River

Si Nan National Park

Southern Nan mountain-and-river country — Doi Samer Dao, Pha Chu and the Nan River corridor toward Pak Nai.

Lam Nam Nan National Park

Reservoir shores and mountain forest linking Nan and Uttaradit.

Phu Soi Dao National Park

Highland pine and meadow landscape on the Uttaradit–Phitsanulok rim.

Namtok Chat Trakan National Park

Multi-tier waterfall country in Phitsanulok’s mountain forest.