Wanchai Sakudomchai, director general of the Meteorological Department, said a new round of cool weather for Bangkok would remain until December 22.
From Sunday to December 22, the morning temperature could drop to 18 or 19 degrees Celsius.
The weather will briefly warm after December 22 before again dropping prior to the New Year holidays, Wanchai added.
He said the mercury will drop because a cold weather mass moved down to central China on Friday and will reach the central, northern and northeastern regions of Thailand on Saturday and Bangkok on Sunday.
He said the rains experienced in Bangkok on Thursday and Friday were caused by the warmer weather and accompanying wind blowing humidity inland.
There could be more rain on Saturday and Sunday before the temperature drop, he added.