Water levels in the Chao Phraya and Noi rivers in Ayutthaya province, which have been steadily increasing since earlier this week, have started to overflow into low plains.
Local authorities have advised people residing near the rivers to monitor the situation closely and move their belongings to higher ground.
Vehicles are now being parked on highway shoulders to escape the flood, while some villagers whose houses have already been inundated have had to live in temporary tents provided by the province.
At Bang Ban canal in Bang Ban district, the newly built water gate has helped keep water flow at the optimum level instead of flooding canal-side communities as in the past.
Authorities however estimate that if the Chao Phraya River keeps rising, the water level might exceed the gate capacity and could flood some of the canal-side areas.