The authorities said heavy rains are continuing in Nan and the situation is worrisome after canals were swollen following forest runoff late Thursday.
By Friday afternoon, more than 200 houses in three districts of Nan including Thung Chang, Pua and Chaloem Phra Kiat were flooded, officials said.
Concerned officials have been ordered to closely monitor the situation as flash floods could occur anytime in low-lying areas.
Meanwhile, Chiang Mai deputy governor Chana Paengpibul has ordered every district in the province to be on alert as heavy downpours continue to devastate the province.
The Meteorological Department has issued a warning that heavy rain would cover between 70-80 per cent of the total area in the province.
Water levels in several canals in six districts of Chiang Mai have risen sharply after heavy rain lashed the province Thursday.
In Doi Tao district alone, a canal overflowed inundating two villages.
Although the situation has returned to almost normal, officials are on alert while they have also been instructed to temporary close national parks and access to waterfalls if the heavy rains resume, officials said.