Flash floods submerged villages as relentless rains hit northern Thailand today.

Runoff cascaded down mountains and swamped large swathes of Phayao province.

The Pong district was among the worst hit areas after rainwater caused the Kham River to spill into low-lying communities.

Officials urged residents along the Kham and Khuan rivers to prepare for evacuations.

In Doi Phu Nang National Park, park rangers were forced to flee as floods surged through the area.

Local authorities said they have deployed rescue teams to assist flood-stricken residents as heavy rain was expected to continue.

The Thai Meteorological Department said a monsoon trough was prevailing across north and northeastern Thailand, with a low-pressure cell lingering over the lower northern region.

Thailand and neighbouring countries in Southeast Asia are in their annual monsoon rainy season which sees soaring temperatures followed by powerful rain storms in the afternoon leading to widespread flash floods.