The Department of Disaster Prevention and Mitigation said summer storms have wreaked havoc to 17 provinces during April 2-6.
Mr Chayapol Thitisak, director-general of the department, said the storms caused damages to 656 homes in 34 districts.
Meanwhile, Bangkok was hit by summer storm last night with heavy rains in many areas until this morning.
Thawi Wattana district was most hit with accumulated rainfall measured at 92 millimetres.
In Lampang, flash flood swept into residential communities in Tambon Bangka of Muang district, causing heavy damages to properties as the muddy water came fast as people were asleep and could not evacuate their properties in time.
Affected villagers said they did not prepare for the forest runoff as it was unusual for the flash flood to occur during this time of the year.
It was the worst flash flood in 10 years, they said.
In Trat province, summer storm fell down several trees on roads. A motorcyclist was slightly injured as his vehicle crashed into fallen trees on the road.
In Phetchabun, a banana plantation in Nong Phai district were damaged by rain storms with more than 5,000 banana trees fell down.
Banana grower Boonthan Singluck, 68, said bananas in his 9-rai plantation were ready for harvest next month, but they were damaged by the summer storm last night.
Mr Boonthan said the storm caused about 300,000 baht damage to his plantation.
According to disaster prevention officials, 17 provinces have been affected by summer storm. They included eight provinces in the North, five in the Northeast, three in the Central, and one in the South.
The Thai Meteorological Department today (April 7) issued summer storms warning for the North, the lower Northeast, the Central including Bangkok and its vicinity, and the East, while the upper South will have more rain.
Affected areas are:
Northeast: Loei, Khon Kaen, Chaiyaphum, Nakhon Ratchasima, Surin, Si Sa Ket, Ubon Ratchathani.
North: Mae Hong Son, Chiang Mai, Chiang Rai, Phayao, Phrae, Nan, Lamphun, Lampang, Tak, Sukhothai, Uttaradit, Phitsanulok, Kamphangphet, Phitchit, and Phetchabun.
East: Nakhon Nayok, Prachin Buri, Sa Kaeo, Chachoengsao, Chon Buri, Rayong, Chanthaburi, Trat.
Central: Nakhon Sawan, Lop Buri, Saraburi, Chai Nat, Uthai Thani, Sing Buri, Ang Thong, Phra Nakhon Si Ayutthaya, Kanchanaburi Suphan Buri, Ratchaburi, Samut Songkhram, Samut Sakhon, Nakhon Pathom including Bangkok and its vicinity.
South: Phetchaburi, Prachuap Khiri Khan, Chumphon, Surat Thani and Nakhon Si Thammarat.
Meanwhile, it said during April 7-9, more rains are expected in the South with high waves of 2-3 metres in the Gulf and the Andaman Sea. All ships should proceed with caution.