Parts of Nakhon Si Thammarat and areas in other southern provinces have been inundated after heavy rains that are forecast to continue this week.
As of Monday, 17 villages in Khanom district of Nakhon Si Thammarat were flooded after days of heavy rain, which affected over 1,200 people in more than 300 households and made 20 roads and six bridges impassable, a source said.
Paiboon Nakthippiman, head of Si Chon district office, said about 10,300 people from 3,450 families were affected by flash floods on Sunday, which began subsiding Monday.
Some low-lying areas, however, were still inundated by remaining floodwater, he said, adding that the overall flooding situation should improve soon if the rain stops.
A survey is being conducted to assess the damage caused by Sunday's floods, he said.
According to a weather notice issued by the Meteorological Department, some light rain is forecast for upper Thailand -- which includes Bangkok and its surrounding provinces -- but further heavy rain has been predicted for the South, which may trigger more flash floods.
The department also said that a high-pressure system over upper Thailand is expected to whip up strong winds and cause temperatures to drop until Sunday.
More rain can be expected in Bangkok on Tuesday, according to the department.
Meanwhile, in Prachuap Khiri Khan, torrential rain from Sunday night until Monday morning has heightened concerns of major flooding across the province.
Kittikon Thepyu-amnuay, head of the province's disaster prevention and mitigation office, said certain parts of Bang Saphan Noi district were slightly flooded, and water levels in the district's main rivers have continued to rise.
Flooding has been reported on the road in front of the district's post office, and Bang Saphan Noi municipality market, he said.
The district has suffered from frequent flash flooding over the past couple of months, he said.
Rising water levels prompted the municipality office to distribute sandbags to people living in flooded areas. The office is currently preparing to evacuate residents if the floods worsen.
As of Monday, more than a hundred families in Bang Saphan Noi district were affected by flooding, said Chitchai Chiwatuwinan, mayor of the Bang Saphan Noi municipality.
Mr Chitchai blamed the floods on delays in the construction of three bridges and the dual-track railway that will run through the district.
About 17 families in tambon Chon Khram in Don Sak district of Surat Thani were also affected by flooding that began on Sunday, when a major canal in the area overflowed.
Flood-prone communities have been warned to stay alert for more flooding as further rain is expected in the South, said Surat Thani governor Wichawut Jinto.