NAKHON PHANOM - Overnight downpours left submerged roads and inundated homes and businesses in this northeastern border province on Sunday, prompting emergency drainage operations.

Wih more rain forecast for the region, the governors of all 14 southern provinces have been ordered to step up flood mitigation preparations.

Heavy falls brought by a monsoon trough stretching across upper northern Thailand and upper Laos lashed Nakhon Phanom from the early hours of Sunday. Rainfall was measured at 107.9 millimetres, with heavy to very heavy rain falling continuously from around 5am.

Floodwater quickly accumulated across much of the municipality as drainage systems failed to cope with hours of intense rainfall. Main and secondary roads were submerged, with water spilling into homes, shops and restaurants. Residents reported damage to household appliances and other belongings, including washing machines, refrigerators, gas stoves and mattresses.

Traffic was severely affected. Many cars and motorcycles stalled while attempting to drive through flooded streets. Officials were helping move stranded vehicles and directing traffic, while residents of several communities sought sandbags to prevent floodwater entering their homes.

The Mekong River rose by 20 centimetres from Saturday, to 10.78 metres, according to meteorological and disaster prevention authorities. Although still 1.22 metres below the river's 12-metre overflow warning level, the elevated water level has slowed the discharge of runoff from tributaries and the city's drainage system into the river.

Some roads in the municipality were reported to be under 30-40 centimetres of water. Authorities warned that further heavy rain could lead to renewed flooding in vulnerable areas.

Stepped-up drainage efforts

Nakhon Phanom governor Adisak Noisuwan and municipal mayor Niwat Jiawiriyaboonma ordered an urgent multi-agency response to tackle the flooding.

At least eight large water pumps were operating at key discharge points along the Mekong River to accelerate drainage from flooded urban areas. Disaster prevention officials, supported by soldiers, were distributing sandbags for use in barriers to affected households and maintaining round-the-clock monitoring.

Teams were dispatched to inspect high-risk areas, clear rubbish blocking drainage grates and provide assistance to residents.

Provincial authorities warned residents in riverside districts of Ban Phaeng, Tha Uthen, Muang Nakhon Phanom and That Phanom, as well as communities near tributaries, to closely monitor conditions. People were urged to move valuables to higher ground and relocate livestock to safer areas if heavy rain persists.

Southern provinces told to prepare

All 14 southern region provinces have been instructed to strengthen flood preparedness.

Deputy government spokeswoman Ploytalay Laksmeesangchan said Prime Minister Anutin Charnvirakul had assigned Deputy Prime Minister Phiphat Ratchakitprakarn to oversee preparedness and response efforts across the South.

She said authorities had been instructed to implement both immediate and long-term water management measures.

The South experiences two rainy seasons, with the Andaman coast typically receiving rain from May to October and the Gulf coast from October to January.

Mr Phiphat has ordered governors in all 14 southern provinces to conduct disaster-response drills, identify evacuation shelters and flood-safe parking areas, and coordinate with state agencies, local authorities and volunteers. Irrigation officials have also been told to manage water releases in line with local conditions.