Thailand's military government has suspended international flights by Thai airlines that have not received new operator certificates from the country's aviation body, a spokesman said.

The measure will affect 12 airlines which together have a market share of only 2 percent and so will have little impact on the country's tourism-dependent economy, the head of the Civil Aviation Authority of Thailand (CAAT) said on Tuesday.

Thailand's aviation industry has been under scrutiny after the U.N.'s International Civil Aviation Organization (ICAO)downgraded the country in June 2015, giving it a red flag for missing a deadline to resolve significant safety concerns.

The government's move comes ahead of an ICAO's visit to Thailand next week.

"They want to see a strict measure. The government had to order CAAT to suspend operations of airlines which did not pass assessment," government spokesman Sansern Kaewkumnerd told reporters.

The Thai military junta often invokes executive power, known as Article 44, to clear bureaucratic hurdles.

CAAT was set up in 2015 by the military government to tackle flaws in commercial aviation. It is tasked with auditing and recertifying Thai commercial airlines to make sure they are in line with ICAO standards.

Chula Sukmanop, director general of CAAT, told Reuters the suspension will affect 12 airlines, including Orient Thai Airlines and Thai Vietjet Air.

"It's not that they failed the assessment, but the assessment has not been completed yet," Chula said.

"They can resume their flights as soon as they pass the assessment," he said, adding that the two airlines are expected to resume their international flights as soon as next month.

The suspension is expected to be lifted for the other airlines by Jan. 31, 2018, Chula said.

The two airlines named were not immediately available for comment when contacted by Reuters.