Phu Sang National Park

A Warm Waterfall in a Northern Forest

There are waterfalls in Thailand that are cold. There are waterfalls surrounded by jungle. Then there is Phu Sang, where naturally warm water flows over a limestone cliff in the middle of a mountain forest.

At the heart of Phu Sang National Park, an underground warm-water source feeds Phu Sang Waterfall. Beyond it, the protected landscape stretches through limestone cliffs, caves, streams, forest and remote viewpoints along the Thai–Lao border.

The park safeguards an important watershed across Phayao and Chiang Rai. For travellers looking beyond the north’s famous destinations, it offers something quieter and more elemental.

Warm water. Wild mountains. A quieter side of Northern Thailand.

Discover. Like. Love. Thailand.

Phu Sang at a Glance

Location

Phayao & Chiang Rai, Northern Thailand

Districts

Phu Sang and Chiang Kham, Phayao; Thoeng, Chiang Rai

Area

178,049.62 rai / approximately 284.88 km²

Elevation

Approximately 440–1,548 m above sea level

Highest Mountain Area

Doi Pha Mon range

Established

2 November 2000

National Park

Thailand’s 98th national park

Border

Thailand–Laos

Signature

Phu Sang Warm Waterfall

Landscape

Mountain ranges, limestone cliffs, forests, caves and streams

Best For

Nature, photography, families, soft adventure and road trips

The Department of National Parks lists the protected area at approximately 178,049.62 rai (284.88 km²). Its Royal Decree was published on 2 November 2000.

Why Visit Phu Sang?

Phu Sang is not primarily a summit to conquer. It is a place to see several natural systems meet:

Mountain → Forest → Limestone → Cave → Spring → Waterfall → Borderland

• A naturally warm waterfall
• Limestone mountains and cliffs
• Caves and geological formations
• Short nature walks
• Ranger-led mountain routes
• Birdwatching and forest wildlife
• Quiet road-trip scenery
• Northern borderland atmosphere

Namtok Phu Sang: The Warm Waterfall

Phu Sang Waterfall is a single-tier waterfall approximately 25 metres high. Its defining feature is the water temperature: commonly reported at around 33–35°C, warm enough to feel surprising when the mountain air is cool.

The water has no strong sulphur smell. It tumbles into a clear, greenish pool surrounded by forest and limestone, creating an intimate experience rather than a vast canyon spectacle.

ThailandLover tip: Visit on a cool morning, when warm flowing water, cool air and green forest reveal Phu Sang’s character most clearly.

How Does a Warm Waterfall Exist?

The waterfall is the final visible stage of a larger geological system. Groundwater moves through the mountain, emerges at a natural warm spring upstream, joins the stream and then crosses the limestone cliff.

Underground water → Warm spring → Stream → Limestone cliff → Warm waterfall

The warm spring environment also supports distinctive vegetation. Research in the park’s freshwater swamp forest recorded a plant community of 16 species, including plants traditionally used as medicinal resources.

A Limestone Mountain Landscape

The park rises from approximately 440 to 1,548 metres and follows the Thai–Lao border for about 30 kilometres. Mountain ridges, limestone cliffs, forested valleys, caves, streams and high viewpoints create a surprisingly varied landscape.

The farther you travel from the waterfall area, the more Phu Sang feels like genuine wilderness.

Mountain, Waterfall & Cave Highlights

Forests & Wildlife

Vegetation changes with altitude, moisture and aspect. The park includes dry evergreen, mixed deciduous, dry dipterocarp, pine and montane forest. Dipterocarps, teak, Lagerstroemia, Pterocarpus, Afzelia and Xylia grow alongside bamboo, wild banana, rattan and ferns.

DNP records wildlife including serow, sambar deer, muntjac, wild boar, northern pig-tailed macaque, langur, lar gibbon, jungle cat, porcupine, civets, reptiles and numerous birds. The Asian giant or elongated tortoise is also associated with the area.

Wildlife sightings are never guaranteed. Treat Phu Sang as a forest-observation destination rather than a safari.

Birdwatching: Bring binoculars, begin early and listen around water sources, forest edges, fruiting trees and quiet trails. Calls often reveal birds before movement does.

Borderland & Watershed

Phu Sang’s mountains form part of the Thailand–Laos border landscape. From high points, views open toward border ridges and valleys. Border areas are controlled zones: remain on designated routes and never approach restricted areas without authorization.

The mountain system is also an important watershed, feeding the Lao, Ngao, Pueai, Bong and Yuan rivers. These waters support farms and communities in Phayao and Chiang Rai.

Forest → Watershed → Agriculture → Communities

When to Visit Phu Sang

November–January · Cool Season

The most comfortable time for walking, photography, accessible caves and mountain viewpoints. Cool mornings make the warm waterfall feel especially distinctive.

February–April · Hot & Dry

Lower elevations become warmer and seasonal haze may reduce mountain views. Begin outdoor activities early.

May–October · Green Season

Forest becomes lush and waterfalls gain flow, but rain also brings slippery trails, wet caves and changing access.

The waterfall flows year-round. Drier cool-season conditions often bring clearer water, while rainy-season conditions create greener forest and stronger flow.

A Perfect Phu Sang Day

Early Morning

Begin at Phu Sang Waterfall while the air is cool and the forest quiet.

Morning

Explore the warm spring area and nearby nature.

Late Morning

Continue to another accessible waterfall, trail or forest area.

Afternoon

If access and conditions permit, join a cave or ranger-led route.

Late Afternoon

Return to the lower park and enjoy the border-mountain scenery.

Doi Pha Dam and remote cave routes need significantly more time and advance arrangements.

Families, Adventure & Photography

For Families

The warm waterfall is relatively close to park headquarters and does not require a major hike, making it suitable for families, older travellers and visitors with limited hiking experience.

For Adventure Travellers

Caves, ranger-led mountain routes, limestone cliffs, forest trekking and remote viewpoints reveal a wilder Phu Sang. Deeper routes require proper planning and should follow ranger instructions.

For Photographers

Warm Waterfall

Include a person or forest context so the image tells the warm-water story rather than looking like a conventional waterfall.

Cool Morning

Look for the contrast between warm water, cool atmosphere and green forest.

Limestone Cliffs

Use a person near the base of the frame to communicate scale.

Caves

Respect lighting rules, never touch formations and allow natural darkness to remain part of the image.

Getting There & Where to Stay

The park’s main visitor area is in northern Phayao, with protected land extending into Thoeng District, Chiang Rai. The waterfall area is accessible via Highway 1093.

From Chiang Kham

Phu Sang is a practical day excursion.

From Phayao City

Allow approximately 100 km or more, depending on your route and chosen attraction.

From Chiang Rai

Approach via the Chiang Rai / Thoeng side; distances vary across this large mountain park.

Phu Sang District

Best for a quiet small-town stay and an early start at the waterfall.

Chiang Kham

A practical base with more accommodation, restaurants, markets and access to surrounding attractions.

Phayao City

Useful for a wider itinerary combining Kwan Phayao + Chiang Kham + Phu Sang.

What to Bring

• Comfortable walking shoes
• Water, hat and sunscreen
• Insect repellent
• Lightweight long sleeves
• Rain jacket
• Small towel and change of clothes
• Waterproof bag
• Headlamp for approved cave routes
• Camera and power bank
• Binoculars

Use proper footwear rather than sandals for cave or mountain routes.

Safety & Respect

Waterfall

Do not enter during unsafe conditions or when park staff advise against it.

Caves

Never enter an unfamiliar cave alone. Rain upstream can alter water levels quickly.

Mountains

Stay on designated routes and follow ranger instructions.

Border

Do not enter controlled or restricted areas.

Wildlife

Observe from a distance and never feed animals.

• Do not remove rocks or fossils
• Do not touch cave formations
• Do not write on cave walls
• Do not pick orchids or wildflowers
• Take all rubbish with you
• Respect temporary closures

Phu Sang vs Phu Chi Fa

Choose Phu Sang

For a warm waterfall, limestone caves, forest streams, geology and a mix of relaxed and adventurous nature.

Choose Phu Chi Fa

For a highland ridge, short summit walk, sunrise and sea-of-cloud photography.

They work well as complementary stops on a northern border-road trip rather than substitutes for one another.

Essential Information

Destination

Phu Sang National Park

Thai

อุทยานแห่งชาติภูซาง

Provinces

Phayao & Chiang Rai

Signature Attraction

Phu Sang Warm Waterfall

Water Temperature

Approximately 33–35°C

Waterfall Height

Approximately 25 m

Geology

Limestone mountains and caves

Other Attractions

Doi Pha Dam, Huai Pong Pha Waterfall, Nam Dan, Nam Lot and Pha Daeng caves

Recommended Time

1 full day; longer for ranger-led mountain or cave routes

Transport

Private or rental car recommended

Before You Go

Access to caves, high viewpoints and remote routes can depend on weather, trail conditions, water levels, conservation measures, border security, ranger availability and temporary restrictions. Contact the park before travelling for Doi Pha Dam or cave routes.

Park Office

146 Moo 8, Phu Sang Subdistrict, Phu Sang District, Phayao 56110

Telephone

+66 93 293 5099

Entrance fees, opening hours and route access can change. Confirm current information directly with the park rather than relying on older third-party listings.