This is the dramatic moment a bridge being battered by a raging river collapsed as heavy rain caused severe floods in southern Thailand.

Footage shows the concrete structure crashing into the raging torrents which had swollen following continuous downpours in Ranong province on December 3.

Disaster warnings were issued in neighbouring Nakhon Si Thammarat province amid widespread flooding from storms throughout Wednesday and Thursday.

Continuous rain and runoff from the Khiriwong mountain sent torrents of water into low-lying areas. Rescue teams are now working to evacuate residents affected by the deluge.

Officials from Thailand Disaster Prevention and Mitigation Department said heavy rain would continue throughout the south of the country until Sunday but Nakhon Si Thammarat had been the worst affected province so far.

Provincial governor Kraisorn Wisitwong declared all 23 districts of the region a ‘disaster zone’ on Friday morning December 3.

Thailand and other countries in Southeast Asia such as Malaysia, Indonesia and the Philippines are nearing the end of their tropical monsoon rainy season, which last until late November. Soaring temperatures reaching 35 degrees Celsius are often followed by powerful tropical storms with thunder, lightning, rain and flash floods which cause rivers to flow faster and become dangerous.

Many of the under-developed nations struggle to cope with the heavy rain due to under-investment infrastructure.