The unusual move is designed to boost the ecosystem in the Gulf of Thailand.
The rusting collection of trucks and 25 disused Army tanks are intended to form an artificial underwater structure to provide shelter for marine life and boost local fish stocks.
The vehicles were lowered into the sea off the Narathiwat coast by crane on Monday.
A wide-ranging marine conservation policy is being enacted in Thailand to preserve fish stocks and keep the seafood industry afloat.
The fertile waters of the Gulf of Thailand are crucial to the nation