Nakhon Si Thammarat municipality was inundated with flood water Thursday after heavy downpours that have claimed six lives in the South since Saturday.
Among the flood-ravaged communities are Pratu Khao, Phaneid, Sareebutr, Ramkaew and Tha Pho.
Authorities sealed off local roads engulfed by flood water while locals moved their belongings to higher ground.
Schools in municipal areas were closed and public buildings and official premises were turned into evacuation centres to accommodate victims of the floods.
Runoff has also overflown across the province, particularly in Nop Phi Tham district where many households were left isolated as main roads became untraversable.
Local authorities were struggling to combat the floods given the volume of water, with 11 water pumps insufficient to flush all the water out to sea.
As of Thursday, water levels were measured at 330mm in Tha Sala district, 260mm in the central Muang district and 240mm in Nop Phi Tham.
Several tambon in Thung Song district were engulfed by overflowing canals Thursday as a result of flash floods over the Banthat mountain range.
Thung Song municipality was submerged under 50cm of flood water and all schools were shuttered.
Disaster and mitigation officials along with rescue workers were sent to help.
Railway officials were also monitoring the situation at Wang-Kapang station as the site was inundated earlier this year.
Officials said if the tracks were submerged, all trains to the southern province of Trang would be cancelled to ensure passenger safety.
Suksawat Sukwanno, director of Nakhon Si Thammarat Airport, waved away rumours the airport was planning to close due to the flooding, insisting everything was operating as normal.
Five water pumps were installed at the airport and large sand bags were put in place in flood-prone areas.
Other southern provinces are also reeling from floods including Narathiwat, Pattani, Phatthalung, Songkhla, Surat Thani, Trang and Yala, according to Chayapol Thitisak, director-general of the Department of Disaster Prevention and Mitigation.
More than 385,000 people in 2,540 villages have been affected.
In Songkhla, the water levels were rising in Ranot, Krasae Sin, Sathing Phra, Singha Nakhon districts due to overflow from Songkhla Lake.
More than 100 rai of rice paddy has also been devoured by flood water, with villagers using boats to navigate their way between communities.
Among Trang's 10 districts, Huai Yot, Kantang, Muang, Na Yong, Palian and Wang Wiset were the most affected by flood water.
In Phatthalung, the six districts of Kong Ra, Sri Banphot, Sri Nakharin, Tamot, Pa Phayom and Pa Bon suffered due to flash floods.
Meanwhile, the Royal Irrigation Department is preparing to ask the cabinet to approve a budget of 14 billion baht to tackle flood-related problems in the southern provinces, according to Thongplew Kongchan, the department's acting director-general.
