Prime Minister Prayut Chan-o-cha has reasserted the need for state quarantine for all Thais returning to the country so authorities can keep a close eye on their health and stem the threat of imported coronavirus cases.
The Interior Ministry on Sunday also ordered all provincial governors to make sure local quarantine facilities are ready.
Taweesin Visanuyothin, spokesman for the Centre for Covid-19 Situation Administration (CCSA), said the 14-day state quarantine is applied to every Thai arriving from abroad.
Those seeking to return will have to comply or they will not be allowed into the country.
He said the measure is needed because travellers from abroad are considered to be high risk even if they are issued fit-to-fly certificates and pass temperature screenings.
"For those who come from abroad, if we let our guard down and just one or two [with infections] slip through, it can become a super-spreader case. We don't want to use this word, but we've learned our lesson," he said.
Dr Taweesin also thanked the 152 Thais who fled state quarantine on Friday for their cooperation after every one of them later reported to authorities as requested.
On April 3, a total of 158 Thais arrived at Suvarnabhumi airport on five flights -- three from Japan and one each from Singapore and Qatar. Health officials explained they were required to undergo a 14-day quarantine at facilities arranged for them by the state under the emergency decree.
But only six of them agreed to be sent to a hotel in Bangkok, a quarantine location prepared by authorities. The 152 others were said to have refused to cooperate, saying they had not been informed about it in advance, and a commotion erupted.
The government later threatened them with arrest unless they reported for quarantine, which all have now done. Dr Taweesin said all returnees would receive proper care during their quarantine at state-designated facilities.
The CCSA spokesman said the quarantine process for almost 100 Thais who arrived on two flights, from Malaysia and Qatar, on Saturday went smoothly thanks to better collaboration among state agencies. It took just three hours to send them to quarantine venues.
Dr Taweesin urged Thais stranded abroad to be patient after the government decided to delay their trips home, saying arrangements were being made to receive them and only a few hundred would be allowed in each day to avoid straining resources.
"We apologise for those left stranded overseas. We need to delay your travel to make sure you will receive proper care when you arrive. An influx is likely to trigger an incident like the one on Friday night," he said.
Last week the government asked Thais to postpone their travel to Thailand until after April 15 as the country prepared quarantine facilities after a rise in local infections linked to imported cases. Entry of foreigners has also been banned.
Public Health Minister Anutin Charnvirakul on Sunday inspected a state quarantine venue at the Royal Thai Air Force facility in Nakhon Pathom's Kamphaeng Saen. The venue is housing 75 people who travelled from Indonesia during April 2-3.
Of those, four have a fever and were sent to Chandrubeksa and Kamphaeng Saen hospitals for testing and observation. Four others who came into contact with them were also sent to hospital.
In Songkhla, provincial authorities on Sunday reportedly held an urgent meeting to prepare for the arrival of some 100 Thais set to return on Monday from a religious event in Indonesia. Under the original plan, the Thai pilgrims were to land at Suvarnabhumi airport. But it was later decided they should be flown into Hat Yai airport for better management and screening processes, as the passengers largely reside in the five southern border provinces.
Meanwhile, Pol Lt Gen Piya Uthayo, assistant police chief and police spokesman, said 308 people were being prosecuted for violating the curfew on Saturday night, the second night of curfew which runs from 10pm to 4am.