“This is a very detailed matter. The Navy needs time to proceed with the information so as to provide a holistic explanation,” Supreme Commander General Surapong Suwana-adth said.

“This kind of information isn’t usually made public. If we reveal what kind of instruments we’re going to equip it with, other [countries] might use more advanced technology against us,” he said. “But I insist that they are essential to create a military balance [in the region].”

Little is known about the Navy’s procurement of the three S26T Yuan-class submarines from China, worth a total of Bt36 billion. Authorities have offered some explanations about their security and economic reasoning as well as broad procurement timelines, but have yet to provide documented details to the public.

Recent speculation was that the hardware would be brought to the Cabinet after the official launch of a submarine port in Chon Buri last month. The junta-backed government, however, said nothing until a week after they had already approved the multi-billion deal in secret. Meanwhile, activist Srisuwan Janya plans to file a petition with the Office of the Auditor-General today to investigate whether the submarine purchase violated the Constitution and relevant laws.

Srisuwan said the procurement could violate the 2017 Constitution, which requires the government to strictly maintain financial and fiscal discipline for public benefit.

He expressed doubts as to whether it was necessary to buy a submarine – not only because of the amount of money it entailed amid the country’s economic downturn, but also its practicality.

“The Gulf of Thailand has an average depth of 25 to 60 metres,” he said. “We’re also not in conflict with any neighbouring countries. There is no reason to accumulate such hardware.”

The procurement process was also far from transparent, Srisuwan said, adding the government had not revealed additional costs such as dock construction, hiring of personnel, supplementary hardware and annual maintenance.

In a related development, most respondents to a Twitter poll conducted by the Nation News Agency (NNA) disagreed with the government’s approval of the submarine procurement. Of the 1,705 respondents, 81 per cent said they disagreed, compared to 9 per cent who backed the green light for the submarine purchase.

Opponents of the plan pointed to the country’s still-weak economy while supporters said the country needed submarines for security reasons.