Namtok Chet Sao Noi National Park

The heart of the park is Huai or Khlong Muak Lek, a natural river about 71 km long. It rises at Khao Inthani in the Dong Phaya Yen range within Khao Yai National Park, flows north as the boundary between Muak Lek and Pak Chong districts, then turns west to join the Pa Sak River in Kham Phran subdistrict, Wang Muang, just below the Pa Sak Jolasid Dam, making it part of the Chao Phraya basin.

Chet Sao Noi Waterfall forms where Khlong Muak Lek tumbles over seven limestone steps. Each tier is only about 2–4 m high but around 20 m wide, and the whole series runs about 490 m. Water flows all year, and tier 4 is considered the prettiest. Because the bed is rock, the water rises quickly when it rains upstream, even if it is dry at the falls.

Sources differ slightly on the falls’ size: some give each tier as about 1–4 m high and the whole series as over 490 m long. Further downstream, Khlong Muak Lek continues as Dong Phaya Yen Waterfall, a broad rock shelf about 1 m high with large shallow pools.

There are several stories behind the name “Chet Sao Noi” (“seven little girls”). One tells of seven sisters who drowned in one of the pools; another says the name combines nearby Ban Sao Noi village with the waterfall’s seven tiers. No document confirms either version.

The forest here is part of Dong Phaya Yen. Silpa Wattanatham explains that it was once called Dong Phraya Fai, after a legend of the hero Khatthakuman lighting a huge fire to lure serpents. In the reign of Rama IV it was renamed Dong Phaya Yen, at the suggestion of Phra Pinklao, because the old name was thought inauspicious and frightening.

Dong Phaya Yen was a major obstacle to building the 265-km Bangkok–Nakhon Ratchasima railway, which took about nine years and ran over budget to about 17.5 million baht; many workers and engineers died of malaria in this stretch. The line went through the pass at Muak Lek around 1898, and Danish assistant surveyor Knud Lyne Rahbek, who died during construction, is buried near Muak Lek station. King Rama V opened the line on 21 December 1900.

In 1955 the construction of Mittraphap (Friendship) Road, Highway 2, made crossing Dong Phaya Yen far easier, cutting the Bangkok–Korat trip from about 10 hours to about 3, and the Muak Lek area grew rapidly.

Muak Lek was once a subdistrict of Kaeng Khoi and became a district on 27 December 1968, opening on 21 January 1969 and moving into a permanent office on 7 May 1970. In 1988 its northwestern part became Wang Muang district. In 1962 Thailand and Denmark set up the Thai–Danish Dairy Farm at Muak Lek, the start of the dairy industry that remains central to the area.

Silpa Wattanatham says the Thai–Danish Dairy Farm grew out of an idea by Danish soil scientist Niels Gunnar Søndergaard, who noticed how little milk Thais drank, together with King Bhumibol’s interest in dairy farming during his visit to Denmark. The farm officially opened on 16 January 1962, and 17 January later became National Dairy Day. Denmark sent experts for the first eight years before Thailand took over and set up the Dairy Farming Promotion Organization of Thailand, which made the country’s first pasteurized milk and, on 2 July 1976, its first UHT carton milk.

The waterfall area was established as Chet Sao Noi Waterfall Forest Park on 21 May 1980, managed at the time by the forest maintenance division. Travel sources note that much of the land had been disturbed and has since recovered through reforestation and natural regrowth.

On 26 December 2016 Royal Gazette volume 133, part 309 Kor, published a royal decree declaring the Thap Kwang forest, Muak Lek forest plot 1 and Dong Phaya Yen forest in Saraburi and Nakhon Ratchasima a national park, effective the next day. It became Thailand’s 129th national park; Thanya Netithammakul, then director-general of the Department of National Parks, called it the first national park of the reign of King Rama X. To celebrate, all national parks offered free entry on 31 December 2016 and 1 January 2017.

The park is covered in tropical forest, with trees such as Burma padauk, wild almond (Sterculia foetida), red silk-cotton, Garuga pinnata, Senna garrettiana, Holarrhena pubescens and Fernandoa adenophylla, while big banyans grip the rock along the stream. Recorded wildlife includes serow, golden jackal, yellow-throated marten, porcupine, pangolin, Burmese hare, flying squirrels, black baza, monitor lizards, Burmese python and birdwing butterflies.

Besides the main falls there are Ko Si Chang Waterfall about 1 km away, Siriphop Waterfall, the “Saphan Kham Phak” (cross-region bridge), a footbridge over the stream that marks the Saraburi–Nakhon Ratchasima border, the “Lan Nap Dao” campsite, a nearly 2-km loop trail along both banks, and a tree tunnel over 200 m long on Highway 2089 (Muak Lek–Wang Muang).

Downstream, the Muak Lek Dam was built in 2012–2020, forming the Muak Lek Reservoir to irrigate Wang Muang district. In 2020 the park sought funds for a new campsite beside the reservoir.

The Muak Lek Reservoir lies in Nong Yang Suea subdistrict, Muak Lek. Its earth dam is 44 m high and 1,157 m long, holding over 61 million cubic metres across more than 25,500 rai, for farming, household use and tap water, and to ease floods in the Pa Sak basin. A road along the crest is popular with cyclists, and a hilltop viewpoint looks out to the Pa Sak Jolasid Dam.

The park is a pilot site for universal design, adding accessible toilets and ramps from 2013 and pushing for wheelchair-friendly design from 2014. On 17 February 2020 a ministerial representative, the chair of the Universal Design Foundation and more than 20 wheelchair users tested the routes. Ramps now reach tier 4 and a viewpoint on the Nakhon Ratchasima side, with three wheelchairs to borrow. The upgrade was also made for the IWAS World Games 2020 in Nakhon Ratchasima.

Chet Sao Noi is one of Saraburi’s most popular attractions, with 389,101 visitors in 2019. A Dhurakij Pundit University study of four Saraburi waterfalls (Chet Sao Noi, Muak Lek, Chet Khot and Dong Phaya Yen) rated Chet Sao Noi highest for tourism potential, averaging 4.03 out of 5, with strengths in management, reputation and facilities.

During COVID-19, swimming reopened on 5 December 2020 under “new normal” rules: swimmers booked via the QueQ app or the visitor centre for 30-minute rounds, capped at 40 people at Chet Sao Noi and Ko Si Chang and 20 at Siriphop.

Flash flooding is the main risk, and the park closes when water runs high. On 31 August 2026, for example, after heavy rain in Muak Lek the night before, the Saraburi branch of Protected Area Regional Office 1 suspended all activities at tiers 1–7 and Ko Si Chang Waterfall for a day before inspecting and reopening.

The easiest swimming season is roughly November to April, when the water is clear and gentle. In the rains the current is fast and rocks are slippery, so avoid the water after heavy rain. On weekends and school holidays the lower pools fill quickly; arrive before noon and swim only in designated areas.