Floodwaters flowing down the Nan River inundated five sub-districts in Wiang Sa district of Nan province overnight, with water levels reaching between 1.5 and 3 metres and marooning over 1,000 households.
As the final bottleneck for mass runoffs originating from Pua, Tha Wang Pha and Muang districts before heading downstream into the Sirikit Dam reservoir, Wiang Sa remains under close watch.
On Friday morning, the surging Nan River at the N.13A station in Ban Boonnak backed up drainage systems and overflowed into communities, including Klang Wiang, Nam Pua, and Tan Chum sub-districts.
Low-lying areas saw floodwaters rise to three metres, cutting off small vehicle access to several villages.
In Nam Pua sub-district, people in single-storey residences, mostly vulnerable individuals, elderly citizens and young children, were evacuated to a temporary shelter at Ban Huai Kaeo, after opting to leave their homes on Thursday over fears of rapidly rising water.
While water levels in parts of Ban Huai Kaeo receded overnight, prompting early morning clean-ups, surrounding areas in Nam Pua, Tan Chum, Klang Wiang and Lai Nan sub-districts face severe flooding.
Meanwhile, in Muang district, low-lying areas, such as the Ban Phaya Phu community, remained submerged under roughly a metre of floodwater on Thursday night.
Rescuers from the Ruamkatanyu Foundation waded through a 500 metre stretch of water before switching to flat-bottom boats to deliver food and medicine to elderly and bedridden residents trapped inside their homes.
Rescuers noted that nighttime relief operations proved particularly hazardous due to poor visibility and submerged obstacles.
Disaster monitoring applications relying on GISTDA satellite data highlighted widespread "high risk" zones across the lower North on Thursday night.
Severe flood warnings remain active across major swathes of Sukhothai and Phitsanulok provinces, with zones at risk spreading into neighbouring Uttaradit and Phichit provinces.
