The Thai Meteorological Department also forecast on Monday that the southwest monsoon will become stronger from Thursday to Saturday and bring more rain across the country.
The department forecast heavy rain for the North, East, South and Central regions and warned of flash floods and runoffs, especially along waterways near foothills and lowlands.
Meanwhile, the Bangkok Flood Prevention Centre reported on Monday morning that light to medium rain had been reported in Don Muang, Sai Mai, Lak Si, Bang Khen, Bang Sue, Chatuchak, Lad Phrao, Dusit, Bang Phlat, Taling Chan, Bangkok Noi, Phasi Charoen, Bangkok Yai, Chom Thong, Thung Khru, and Bang Na.
Scattered thundershowers with isolated heavy rains have been forecast for Greater Bangkok this week. The temperature is expected to vary between lows of 24-28 degrees and highs of 32-36 degrees Celsius.
The North, meanwhile, will see isolated to scattered thundershowers all week, with temperature lows of 22-27 degrees and highs of 30-37 degrees Celsius.
The Northeast will also see isolated to scattered thundershowers until Wednesday and fairly heavy rain for the rest of the week. Temperature lows of 22-27 degrees and highs of 30-37 degrees Celsius have been predicted.
The Central region will see isolated to scattered thundershowers on Monday and isolated heavy rain until Saturday. Temperature lows of 22-27 degrees and highs of 31-37 degrees Celsius are expected.
The East will see fairly widespread thundershowers with isolated heavy rain on Monday and Tuesday and scattered thundershowers for the rest of the week. Metre-high waves have been forecast on the eastern coast of Thailand, which will rise higher in thundershowers. Temperature lows of 23-28 degrees and highs of 29-36 degrees Celsius have been predicted.
Scattered thundershowers with isolated heavy rain have been forecast for both the east and west coasts of the South of Thailand.
Waves are expected to be about 1-2 metres high and higher in thundershowers.
The temperature in the South is expected to vary between lows of 22-27 degrees and highs of 30-36 degrees Celsius.