Chon Buri, including tourist mecca Pattaya, has been declared a disaster area following heavy flooding after the area was lashed with rainfall on Wednesday night and Thursday.
Citywide flooding reached 30 centimetres after just 45 minutes.
Wednesday's deluge, caused by tropical storm Vamco, continued all day and into the night, leaving most parts of Bang Lamung district under a metre or more of water.
A woman stands inside her flooded grocery store waiting for the water to recede in Pattaya. (Photos by Chanat Katanyu and Pattarapong Chatpattarasill)
The Friday morning enhanced satellite view of the Asean region by Meteorological Service Singapore shows Vamco still active over western Cambodia and Central Thailand, but moving slowly away into the Bay of Bengal.
Pattaya mayor Ittipol Khunpluem said the disaster declaration would help accommodate state relief and assistance to the area despite the fact that most of the flooding had subsided.
Tourism activities in Pattaya were continuing except at sea, he said.
However, authorities are closely monitoring the weather since rainfall has continued to a certain extent, Mr Ittipol said.
Storm surges and high-level roads are the main factors blocking water drainage in Pattaya and nearby Rayong, causing heavy flooding to wreak havoc in many parts of the area, an expert said.
Hydro and Agro Informatics Institute (HAII) director Royol Chitradon said high water levels had impeded storm water from flowing into the sea, causing continual sewage flooding in Pattaya and central areas of Rayong.
Drainage problems in the coastal provinces happen when flood-prone areas are hit by storms and heavy rains every year, he said.
In addition, high-level roads blocked water drainage.
On Thursday, the government declared four other provinces disaster areas after they were battered by downpours caused by the tropical storm.
A vehicle torn away by the flood waters lies upside down at tambon Huai Yai in Chon Buri.
In Rayong province Thursday morning, heavy rain caused a dyke at Klong Bang Phai reservoir to burst, resulting in a flood of 50-100cm in Yai Ra village of tambon Samnakthon in Ban Chang district.
The other provinces declared disaster zones were Trat, Chanthaburi, Surin and Si Sa Ket which was the worst hit, Interior Minister Anupong Paojinda said.
The storm continued to lash 14 tambons, eight districts in the five provinces in eastern and northeastern regions, inundating houses, sweeping stores and sinking trawlers and leaving tourists stranded on an island in Chon Buri province.
The Meteorological Department reported that Vamco had "lost steam" and was downgraded to a low-pressure cell. But its remnants, coupled with the monsoon over the Andaman Sea, the South and the Gulf of Thailand will continue to bring heavy rain to some areas today.
People in many provinces have been warned to beware of flooding: Nakhon Nayok, Prachin Buri, Chon Buri, Rayong, Chanthaburi, Trat, Bangkok and surrounding provinces, Phetchaburi, Prachuap Khiri Khan, Chumphon, Ranong, Phangnga, Phuket, Trang, Krabi and Satun.
Teams of army officers are helping villagers move their belongings to higher ground in flood-hit areas.
