The Royal Thai Navy has secured 13.5 billion baht to purchase a Chinese-made submarine.
It is expected the vessel would be ready to enter service in six years time.
Navy spokesman ACM Jumpol Loompikanon said the money has been included in the 2017 Budget Bill approved by the National Legislative Assembly.
The purchase of the Yuan Class S26T, the first of three Chinese-made submarines which the navy intends to acquire at a total cost of 36 billion baht, should be made this year, he said.
If all goes to plan, Thailand will have its first submarine in service since the early 1950s, he said.
Four small Japanese-made submarines purchased in 1938 were decommissioned in 1951.
The Chinese S26T craft has a submerged displacement of 2,600 tonnes and is equipped with an air-independent propulsion system that allows the submarine to stay under water for up to three weeks at a time, according to the navy.
This first submarine will cost considerably more than the other two -- which will be purchased later -- because the 13.5 billion baht will also cover weapon system costs, training courses for the crews, visits by Chinese personnel and various maintenance costs, ACM Jumpol said.
Procurement of the first Chinese submarine will be conducted in a government-to-government deal after the cabinet gives its final approval to the contract.
The navy's intention to purchase new submarines, a proposal it has made under successive governments, has sparked public debate.
Many people think they are unnecessary and would be a waste of money.
Other critics have even questioned whether the Gulf of Thailand is deep enough for submarines to operate in.
The navy has responded to these remarks by claiming it needs to protect the national interest and match the naval defence capabilities of neighbouring countries.
According to regional security sources, Malaysia now has two submarines, while Singapore has four and is about to purchase two more.
Vietnam has six and Indonesia is in the process of replacing two old German-made submarines with three new ones from South Korea.