Bangkok escaped severe torrential downpours after the much-hyped Gaemi storm, which was downgraded to a low pressure system, caused only moderate rainfall in the capital Monday.
Government agencies, however, will be on standby for possible flooding in the city's at-risk areas until tomorrow.
Average rainfall was measured at 60 millimetres in Bangkok Monday, well below the 90mm predicted earlier.
Rain fell on all 50 districts of Bangkok, with reports of minor flooding in some traffic lanes.
The Disaster Prevention and Mitigation Department yesterday reported that flooding is now affecting 40 districts in nine provinces, comprising Prachin Buri, Chachoengsao, Phitsanulok, Phichit, Ang Thong, Ayutthaya, Suphan Buri, Nakhon Pathom and Samut Prakan.
Meteorological Department deputy director-general Somchai Baimuang said the low pressure cell was moving in a westerly direction toward Nakhon Pathom, Ratchaburi, Kanchanaburi and finally the Andaman Sea.
There will be no storm surge as feared, he said, adding that normal weather is expected to return tomorrow.
Royol Chitradon, from the government's Water and Flood Management Commission, said the storm Phra Phiroon, which is forming east of the Philippines, would not affect Thailand.
However, he said fishing boats are advised to proceed with caution and small boats should remain in port because of possible high waves.
Royal Irrigation Department director-general Lertviroj Kowatthana said Bhumibol and Sirikit dams should be at only 73% of their capacity when the rainy season ends later this month.
Less-than-expected rainfall from the Gaemi depression has prompted government agencies, especially in the Northeast, to begin considering reserving water in dams for the next dry season.
Piyachat Insawang, chief of disaster relief in Nakhon Ratchasima, said Gaemi had not brought much rain and the Lam Takhong reservoir in Sikhiu district now held only about 47% of its capacity.
Without additional inflow, she said, local people would suffer from drought.