Transport Minister Arkhom Termpittayapaisith has told airlines with frequently delayed flights to improve operations.
The minister asked the Civil Aviation Authority of Thailand (CAAT) to act against airlines with troubled flight schedules, with CAAT chief Chula Sukmanop admitting embattled Nok Air was among the worst offenders.
Mr Chula said Monday the agency had not decided whether to suspend Nok Air flight operations as he will wait to talk to its executives this week to determine the reasons behind the persistent problems.
In February, the airline experienced a severe shortage of pilots which led to a pilot strike amid accusations that pilots were forced to exceed standard flight hours.
The shortage problem appeared to return last month, Mr Chula said, so "we need to talk with the airline" before taking further action.
Nok Air executives could not be reached for comment.
Mr Arkhom said planes must always be ready for service. Airlines responding to delays by providing assistance to customers shows a sense of responsibility, but delays are "unwanted".
The CAAT wants to ensure all airlines serve passengers on schedule and this can occur if they adopt adequate maintenance programmes to prevent technical problems, he said.
Nok Air is also among Thai-registered airlines which are required to go through the re-inspection of their Air Operator Certificates (AOCs), after the International Civil Aviation Organisation (ICAO) in June last year issued a "red flag" that indicates significant safety concerns.
Authorities started the re-issuing process of AOCs for 25 airlines last month, Mr Arkhom said.
He reported progress to the ICAO during a recent conference at its headquarters in the Canadian city of Montreal last month, saying ICAO executives were "satisfied with our solutions".
One solution was to split the now-defunct Department of Civil Aviation into the CAAT and Department of Airports after the ICAO noticed a conflict of interest in the department's role as supervisor and a service provider.
Under the new structure, the CAAT assumes a regulatory role.
As for the certificates, Mr Chula expected new AOCs to be granted to the first batch of seven or eight airlines between January and February.
By March, the CAAT believes it will finish 75% of the re-inspections. It will then ask the ICAO to conduct new airline audits, he said.
In another development, Mr Chula said the US Federal Aviation Administration (FAA) should upgrade Thailand from aviation security Category 2 to Category 1 next year. The FAA earlier noted a lack of qualified experts to issue licences for new pilots, causing the downgrade.
A new inspection is needed for more than 1,000 pilots, he said, expecting a "return to Category I as soon as March".