All passenger flights have been banned from landing in the country to curb the outbreak of the new coronavirus, the aviation agency said on Friday.
The ban came into effect on Saturday morning and will run until the end of Monday, the Civil Aviation Authority of Thailand said in an order published late on Friday.
Anyone arriving on a flight that took off before the order came into effect will need to be quarantined for 14 days upon arrival in Thailand, the order said.
It came just hours after a commotion at Suvarnabhumi airport when more than 100 Thai nationals arrived on different flights on Friday, a Immigration Bureau officer told Reuters.
"A public health officer allowed them to quarantine themselves at home. There was a commotion because they said they weren't aware they had to be put in a state quarantine," the officer said.
Thailand, which has reported 1,978 cases of the coronavirus and 19 deaths so far, wants to avoid importing more cases.
Since March 1, there has been a rising number of people who were infected abroad before returning home. The authorities have put nearly 2,000 people who came into contact with them in quarantine.
The ban on incoming air travel came a day after the government asked citizens abroad to delay returning home until after April 15 in a bid to stop imported cases.
Thailand has six international airports, including in the capital Bangkok, which is under a curfew from Friday, and the popular tourist island Phuket, which was planning to shut its airport from Friday to April 30.
Earlier on Friday, the country reported 103 new coronavirus cases and four more deaths.