🔄 Updated 21 Jun 2026
Say Phayao and most people picture Kwan Phayao and the lakeside cafés. But drive on north toward Phu Sang district for another hour or so and you reach Phu Sang National Park, a large stretch of forest along the Laos border that stays quiet, isn't crowded yet, and has something you won't find elsewhere — a waterfall whose water is genuinely warm. It isn't a sulphur hot spring; it's a clear stream running down a limestone cliff, holding steady at around 35°C all year.
The park spreads across the Doi Pha Mon range, running through Phu Sang and Chiang Kham districts of Phayao and up into Thoeng district in Chiang Rai — roughly 178,000 rai in total. The part visitors head for is the area around the park headquarters, and the waterfall is only about 300 metres away from there, an easy walk.
Phu Sang Waterfall, the only warm one in Thailand
Phu Sang Waterfall is small, around 25 metres high, tumbling down the limestone cliff in tiers. What makes people set out to see it is that the water is warm, about 35°C. It's clear, with none of the sulphur smell of a hot spring, so you can comfortably wade in and play — especially in the cold season when the air outside is chilly but the water in the pool stays just right.
The warmth comes from a seep pool above the falls. Water rises from underground through the limestone and then runs down as the waterfall, which is why it holds a steady temperature all year and doesn't swing up and down with the weather. There's space in the pool at the base to soak; the water isn't very deep, so it suits families bringing kids to splash around.
When the soak feels best
The cold season (Nov–Feb) is when the warm-waterfall feeling lands hardest — the air outside is properly cold, so stepping into the warm water feels strikingly different. In the rainy season the flow is stronger and murkier; the warmth is still there, but it's harder to actually swim.
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Three nature trails
Phu Sang isn't rough country you need to prep hard for. Most of the trails are short nature loops you can walk without a guide, looping back to where you started — good for anyone who wants forest air without wearing themselves out. There are three to choose from.
- Phu Sang Waterfall trail, ~1,700 m — follows the stream up from the falls to the seep pool at the source, where you see where the warm water comes from alongside damp evergreen forest beside the creek. It's the popular one because it's close and connects neatly to the waterfall.
- Huai Miang trail, ~1,400 m — the shortest, passing through miang forest (the old tea of northern Thais). An easy walk, good as a warm-up.
- Huai Sai trail, ~2,400 m — the longest, going deeper into the forest, with a wider range of plants and birds. Best for anyone who wants a slightly more serious walk.
Each trail takes about 1–2 hours depending on your pace. The paths are mostly dirt and rock, with a few spots that get slippery in the rainy season, so shoes with decent grip make the walk easier.
Hiking safely
Let the rangers know before you take the longer trail, and carry your own drinking water — phone signal in the forest is patchy. In the rainy season watch for leeches and slick footing; a spray of insect repellent before you set off helps a lot.
Other spots inside the park
The seep pool (warm-water source)
The source of the waterfall, where water rises from underground through evergreen forest and freshwater peat swamp. This is the spot that explains why the falls are warm, and it's a short walk up from the waterfall.
Pha Daeng Cave
A large limestone cave about 450 metres deep, with handsome stalactites and stalagmites, also within the park. Check with the rangers about access and lighting before you go.
Doi Pha Mon (sea of mist)
The mountain range the park runs through. In the cold season there's a sea of mist and sunrise viewpoints, over on the Chiang Rai side — worth adding if you have the time.
A 2-day, 1-night Phu Sang plan
Phu Sang is a fair distance from Phayao town (about 1.5–2 hours), so a there-and-back day trip feels rushed. Camping one night gives you the forest in the early morning, with the thin mist, far more fully.
Arrive at Phu Sang, soak under the falls, an easy walk
Morning forest, stop in Chiang Kham on the way back
Fees, opening hours, getting there
- Opening hours — open to visitors roughly 6am–6pm (the office / visitor services run about 8am–5pm).
- Entry fees — Thai adults around 10 THB, children 50 THB; foreign adults 100 THB, children 50 THB; car around 20 THB.
- Camping — there's a campground in the park, with tents and bedding for rent, toilets, charging points, and a restaurant nearby.
- Location — Phu Sang district, Phayao province, reached via Highway 1021, about 1.5–2 hrs from Phayao town and around 30 km from Chiang Kham.
- Contact — call the park headquarters before you go, especially if you plan to stay overnight or enter Pha Daeng Cave.
The easiest way to get there is to drive yourself, since public transport barely reaches it. The route from Phayao town runs through Chun and Chiang Kham districts on good roads the whole way, with a short stretch of mountain climb near the end. You can also come in from the Thoeng side in Chiang Rai.
Pack before you go
Bring a swimsuit or clothes you don't mind getting wet, a towel, hiking shoes, a warm jacket if you're coming in the cold season, and cash — many of the spots in the forest don't take transfers, and the signal isn't reliable.
Plan a full Phayao trip — the lake, the temples, the cafés, and the Phu Sang forest
See the Phayao travel guide →