The captain of the Nok Air flight that slid off the runway at Chiang Rai airport will be summoned by regulators to explain why passengers were kept on board the aircraft for about an hour after the accident.
Suttipong Kongpool, director general of the Civil Aviation Authority of Thailand (CAAT), said on Monday that the chief pilot of flight DD108 will be ordered to defend the decision.
"The rationale behind the decision is what the CAAT needs to hear from the captain," Mr Suttipong told the "Inside Thailand" news programme.
The Don Mueang-Chiang Rai flight with 164 passengers and six crew slid off the runway and its undercarriage collapsed as it landed in heavy rain at Mae Fah Luang in the northern province on Saturday night. There were no injuries.
The captain turned off the engines of the 737-800 Boeing aircraft after the accident, leaving the passenger cabin in darkness and without air conditioning.
The passengers were then told to stay on board until buses arranged by the airline arrived to take them to the terminal.
After about an hour fewer than 20 passengers had left by vans. The remaining passengers started complaining about the stuffy conditions in the cabin, the lack of fresh air causing breathing problems and the possible dangers of staying in their seats in the dark.
In a video taken by a passenger in the cabin, a woman crew member was heard trying to calm down the angry passengers and telling them to remain seated. She said, "Passengers are not allowed on runways."
The passengers insisted on leaving the plane and the captain eventually permitted one of the eight emergency exit doors to be opened so they could disembark on a slide.
Under international aviation protocols, all passengers must be evacuated from the aircraft within 90 seconds of a serious incident, according to the CAAT chief. But the evacuation rules were also flexible, depending on the circumstances and safety of the passengers and aircraft, he said.
"The captain is the one who makes the decision on evacuation after assessing the situation, including external factors," Mr Suttipong said.
The CAAT chief also said passengers were allowed to stand on runways in case of emergency, although they were off limits in normal circumstances.
It was not known whether the captain was a man or a woman.
Mr Suttipong said the aviation regulator would not be quick to blame the chief pilot for the slow evacuation that kept most passengers inside the aircraft without sufficient air to breathe. Heavy rain and the need to wait for the buses could be among the reasons for the decision, he said.
Nok Air has also not explained the decision.
Nok Air chief executive Wutthiphum Jurangkool told the Stock Exchange of Thailand in a filing on Monday that the airline was in compliance with all aviation safety guidelines to ensure the safety of all passengers. The airline would investigate the accident, he said.
Mae Fah Luang airport management said on Monday the airport strictly followed emergency procedures after the accident on Saturday night. This included the quick dispatch of fire engines to the aircraft and the closure of the runway for the safety of other airplanes.
The airport remains closed until Wednesday, while the Boeing jet is removed and the runway examined for damage.