Officials rushed to neutralise nitric acid leaking from plastic containers on board a truck in Ayutthaya on Monday morning.
The accident happened on a road near Factory Land Industrial Estate in the Wang Noi district.
The powerful acid caused several people nearby to experience eye and nose irritation.
Charoenkwan Kaewthongrat, an Ayutthaya industry official, rushed to the scene following the accident and workers were soon employing sodium carbonate to neutralise the acid that had leaked.
Boonsong said some plastic tanks leaked when the truck was descending from a bridge at a high speed, causing a road spill of about 300 metres long.