The Bangkok Metropolitan Administration has put all 50 districts in the capital on alert for possible flooding, Bangkok deputy governor Malinee Sukvejvorakij said on Thursday.
The weather forecast is for heavy rain in many parts of the country including Bangkok between Sept 14 and Sept 17.
Dr Malinee said all districts were told to install water pumps in flood-prone spots, so that rainwater could be quickly drained away.
People in 27 communities, involving more than 1,200 households in 13 districts, not protected by floodwalls along the Chao Phraya River should be ready to remove their belongings to higher places.
The BMA had earlier drained water from some major canals, including Khlong Saen Saep, particularly the parts running through Phetchaburi, Sukhumvit and Khlong Tan roads.