Floodwaters remained high at 10.30am, leaving several cars partially submerged. Motorists were warned to avoid the area as water on roads was too deep for cars and motorcycles to pass.
The Department of Meteorology forecast heavy rain for 60 per cent of Bangkok and its vicinity today.
It also projected lows of 25-27 degrees Celsius and highs of 34-38C.
The wind speed is 10-25 kilometres per hour.