Rain came down in several districts in Bangkok, Nonthaburi, Pathum Thani and Samut Prakan on Friday morning.
The Bangkok Metropolitan Administration and traffic radio stations reported rain in most parts of Thon Buri and some inner districts of the capital including Phaya Thai.
By rush-hour time, the storms were also pouring rain in eastern Bangkok regions including Bang Na. Earlier, City Hall said that Bang Khae district was hardest hit by the early morning downpours.
Phetkasem road in Bang Khae was flooded and traffic congestion was reported in Ramkhamhaeng, Lat Phrao and Ratchadaphisek areas, according to Jor Sor 100 and FM91 Traffic Police radion stations.
The Meteorological Department expected summer storms to pound the Bangkok region through Saturday.