Prime Minister Prayut Chan-o-cha will make a decision about whether Thailand will be forced back into another lockdown if the Omicron variant of Covid-19 is detected in the country.
However, the new strain has not been found in Thailand yet, according to health authorities.
Speaking after Tuesday's cabinet meeting, Deputy Prime Minister and Energy Minister Supattanapong Punmeechaow said the cabinet instructed relevant agencies to monitor the situation closely while the Public Health Ministry will assess the country's reopening in two weeks' time.
Deputy Public Health Minister Sathit Pitutecha urged the public not to panic, saying the prime minister has ordered security agencies to intensify border surveillance to prevent illegal border crossings to help keep the virus at bay.
Mr Sathit stressed that officials who are found to be negligent of their duty will face severe punishment.
He told the Bangkok Post that the cabinet did not discuss a lockdown, but considered tougher measures to detect the virus.
The government was concerned about illegal migrants sneaking into the country via natural border crossings, Mr Sathit added.
"The situation will be monitored closely. Measures will be reviewed based on new information coming in. If the Omicron strain is found in Thailand, the country will have to face another lockdown," Mr Sathit said. "It is the prime minister's policy and he will make a quick decision as director of the Centre for Covid-19 Situation Administration [CCSA]."
Mr Sathit also said that nightlife venues may be allowed to reopen on Jan 16 if the Omicron strain is not detected, though he stressed the need to continue following DMHTT guidelines, referring to social distancing, mask-wearing, hand-washing, temperature-checking and using the Thai Chana app.
The Stock Exchange of Thailand Index plunged by 21 points, or 1.32%, to close at 1,568.69 points on Tuesday amid concern of another possible lockdown following the emergence of the Omicron strain.
This prompted government spokesman Thanakorn Wangboonkongchana to allay fears of another lockdown, saying the issue was not raised at the cabinet meeting.
"But if the new strain is found in Thailand, the prime minister will be informed straight away," Mr Thanakorn said, adding that the premier ordered all involved to keep a close watch on the situation.
He said the Public Health Ministry is monitoring all mutated strains of the virus and conducting proactive testing of 4,000-5,000 people every week. Strict measures remain in place to screen tourists entering by air, land and water, the spokesman said.
The prime minister also stressed the need for everyone to receive vaccine shots which helps prevent the worst effects of the virus, Mr Thanakorn said.
Deputy Prime Minister and Public Health Minister Anutin Charnvirakul said that scientists worldwide are racing to develop vaccines to cope with the new strain and Thailand is following their progress.
Thai researchers are also developing local vaccines against the new variant, the minister said, adding that the ministry is working to ensure sufficient supplies of vaccines, medical equipment and personnel to prepare for any future emergencies.
Mr Anutin made the remarks as he was attending the special session of the World Health Assembly in Geneva, Switzerland which started on Monday and will end today.
The cabinet on Tuesday decided to suspend the CCSA's plan to allow international travellers to take an antigen test (ATK) instead of an RT-PCR test to enter the country over concerns surrounding the spread of the Omicron variant.
The relaxed requirements, which were supposed to take effect on Dec 16, would have applied to travellers from 63 countries and territories permitted to enter under the test-and-go scheme.