Drivers to the southern region have been advised to take extreme caution as part of Phetkasem Road in Prachuap Khiri Khan was flooded on Monday.
The central province was hit by torrential rain and a runoff, while many southern provinces were still battered by flooding, which ravaged the region since the new year and claimed at least 21 lives.
A flash flood struck Bang Saphan and Thap Sakae districts in Prachuap Khiri Khan on Monday afternoon mainly from the runoff from the Tanaosi mountain bordering Myanmar.
Bang Saphan district chief Sakarin Tumsen said the water level was up to 50 centimetres high in some locations on the highway to the South.
Bang Saphan police decided to close some lanes of Phetkasem and used ropes to alert drivers where a road dividing ditch was located to prevent vehicles from plunging into the ditch.
Thap Sakae district chief Thanapat Na Ranong told the FM91 traffic radio station that people who planned to drive to the South should delay the trip if it is unnecessary due to the flooded road.
Heavy rain also pounded Muang, Kui Buri and Bang Saphan Noi districts in the province.
Bang Saphan Hospital put up sandbag barriers to prevent the place from being flooded and hastily moved some patients to other hospitals.
"We are assessing whether we can prevent the hospital from getting flooded as rain continues to pound the area," hospital director Cherdchai Chayawattato said.
Prachuap Khiri Khan and Phetchaburi are braced for more torrential rain and flash floods until Tuesday, the Meteorological Department warned in the latest statement.
Surat Thani, Nakhon Si Thammarat and Trang were also ravaged by flash floods.
Chatchai Promlert, the director-general of the Disaster Prevention and Mitigation Department, identified nine provinces -- Phetchaburi, Prachuap Khiri Khan, Surat Thani, Chumphon, Nakhon Si Thammarat, Ranong, Phangnga, Krabi and trang -- as risk areas prone to sudden flooding and landslides.
Officials in the nine provinces have to stay alert until Wednesday to evacuate people to high ground if needed, he added.
The private sector has estimated the cost of the severe flooding in the South at no more than 15 billion baht.
Floods kill more than 20 in southern region. (Reuters video)