Some of the heaviest rain to have fallen on Bangkok in two decades has overwhelmed the capital's main canals, making it difficult to drain water from some parts of the city, governor Chadchart Sittipunt said on Wednesday.

Bang Khen district reported 170 millimetres of rain since Tuesday -- the highest in 20 years.

As a result, water levels along Klong Lat Phrao and Klong Prem Prachakon, the district's main drainage canals, have also risen, causing floods in some areas.

Some of the most affected locations include the Bang Khen roundabout and areas surrounding the tracks of a new electric train route, which the governor said was partly to blame for slow drainage.

He said run-off from Pathum Thani was compounding floods in the area.

The Bangkok Metropolitan Administration (BMA) and the Royal Irrigation Department (RID) are doing the best they can to drain the flood water off the city's streets, but high water levels across the city's main canals have made it difficult, said the governor.

With more rain expected today, the public has been advised to plan their trips accordingly.

Mr Chadchart urged motorists to keep an eye on the weather forecasts, as well as flood reports and traffic conditions.

At least 17 locations in Bangkok were flooded from Tuesday night until Wednesday morning, according to the BMA.

On Tuesday night the floods paralysed traffic in certain parts of the city.

Residents living in Bang Khen, Lat Phrao, Don Muang and Chatuchak are advised to prepare as more heavy rain is on the way.