The Department of Civil Aviation (DCA) is defending its safety standards after media reports that the United Nations' civil aviation authority is auditing the department and may downgrade its performance.
DCA director-general Somchai Piputwat said if the department has given an airline the green light to fly, it is fully in line with international aviation safety standards.
However, he admitted the auditors are likely to find problems with a lack of personnel and a "conflict of interest" about the way the DCA operates.
The International Civil Aviation Organisation (ICAO)'s Universal Safety Oversight Audit Programme (USOAP) does not rank aviation authorities and cannot punish transgressors, Mr Somchai said. The audit is a normal practice the agency performs every four to six years.
Recently, however, the ICAO said it would begin assessing civil aviation departments from several Asian nations more stringently after a spate of disasters in the region.
He said the USOAP audit is intended to promote standards and safety among 190 member nations , including Thailand.
He said the ICAO is likely to flag a conflict of interest between the DCA's role as a supervisor and also a service provider.
Its job role is to supervise aviation functions and yet it also provides various services at 28 provincial airports.
The DCA is also short of staff, in part because of low salaries and poor benefits provided to employees.
He would explain to auditors that the DCA does not manage the 28 DCA airports for profit but instead focuses on providing good services to passengers and ensuring national security.
"Personally, I agree the supervisor should be separate from the service provider, but it is not easy for Thailand because the 28 airports are centred on providing a public service, not profit," he said.
The ICAO audit will cover legislation and regulations, organisation and safety oversight functions, personnel licensing, aircraft operation supervision, aircraft accident and incident investigation, and the airworthiness of aircraft.
"Our concern is about the ICAO's way of thinking, which tends to assume that a weak supervising organisation results in weak airlines. That is not always true," Mr Somchai said.
"I can confirm the airlines which passed DCA supervision and inspections are in line with international safety standards."
The ICAO's auditing programme will reveal its result on Saturday.
If it has any recommendations, the department has 15 days to submit a plan to improve its operations and has another 90 days to improve its performance following the plan.