The injured were hospitalised, and two of them were later allowed to go home.
Arkom Wanchalermchai, mayor of the municipality, said the water tank, which has a capacity of 14,000 cubic metres, suddenly burst during testing on Thursday night. A large amount of water then poured out onto nearby homes and farms.
The cost of the damage was estimated to be more than 100 million baht, Mr Arkom said.
Dirt, trees and construction material werre carried out towards the 93 kilometre mark of the Chonburi motorway by the deluge, said Yongyot Wanpradit, director of the District Motorway Maintenance Office.
The highway’s barriers were able to keep the debris away from the traffic lanes, Mr Yongyot said.
Kanyanat Weerapan, corporate communication director of the East Water Group, the company in charge of the water tank’s construction, said the company will take full responsibility for the incident.
Ms Kanyanat said the cause of the water tank burst was being investigated.