Everyone escaped with injuries.
The event occurred on Aug. 15 at Mae Sa Waterfall in Doi Suthep-Pui National Park in Chiang Mai’s Mae Rim District.
Several people were in or near the stream when water from upstream suddenly flooded the place, according to Viral Press.
Footage circulating online shows tourists scrambling across rocks as the current gathers pace. Some were knocked off their feet and carried downstream, while others struggled to reach safer ground.
Park officials and other visitors moved in to help those caught in the flood.
Several of the visitors suffered minor cuts and bruises, but at least one visitor was taken to hospital for treatment, Thai media outlet Khaosod reported.
A visitor who filmed the incident, identified as Arttie Martin on Facebook, said he had been preparing to walk toward the waterfall with a foreign tourist to take photos when he heard a park official blow a whistle.
The warning came just moments before the surge swept through the area, catching several tourists in the water. Martin said the flooding began almost instantly, leaving little time for those in the water to react.
The waterfall was quickly closed to visitors as authorities assessed the safety of the site following the flooding.
Northern Thailand has been experiencing periods of heavy rain, increasing the risk of sudden flooding and runoff in mountainous areas.
The incident brought renewed warnings about the risks of visiting waterfalls during Thailand’s rainy season, when water levels can rise rapidly if there is rainfall upstream.
The government’s tourism website advises visitors to leave waterfall areas immediately if the water becomes cloudy as this can signal an approaching flash flood.
It also urges tourists to follow warnings that are posted and avoid climbing rocks or entering restricted sections of streams.
Mae Sa Waterfall, 30 kilometers from Chiang Mai, is a popular natural attraction known for its multi-tiered cascades and lush forest setting.