BANGKOK • Thailand's military government has approved spending of 13.5 billion baht (S$543 million) to buy a submarine from China after putting the purchase on hold last year, Thai officials said yesterday.

Relations have been strengthening between China and America's oldest ally in South- east Asia, particularly since ties with the United States cooled after a 2014 coup.

The purchase of the submarine was put on hold last year in the face of public criticism and questions as to whether Thailand really needed a submarine.

Thai navy officials said negotiations with the Chinese government were nearly finalised and the budget had been earmarked to pay for the submarine over six years.

"We are in the process of negotiating, but this year there will definitely be a signing agreement as we have the budget," said Navy spokesman Jumpol Loompikanon.

Admiral Jumpol said the submarine would allow the navy to study tactics and how submarine warfare may be used against Thailand.

Maritime security is a hot issue in South-east Asia given the competing claims over the South China Sea, but Thailand is not involved in that dispute.

The Thai army has also set aside two billion baht over three years to buy 10 tanks and auxiliary vehicles from China, according to General Chatudom Thittasiri, deputy permanent secretary at the Ministry of Defence.

The purchase is in addition to 28 main battle tanks ordered from China last year.

China was the first major power to acknowledge Thailand's ruling junta following a 2014 coup.

The US responded to the military coup by freezing US$4.7 million worth of security-related aid and cancelling some security agreements.

REUTERS