Prime Minister Srettha Thavisin said he had instructed the armed forces to secure the border with Myanmar and not allow any military aircraft from the neighbouring country to enter Thai airspace as fighting there has intensified.
Mr Srettha said that he was briefed about the situation along the Thai-Myanmar border by army chief Gen Charoenchai Hinthao. "Everything remains under control," the prime minister said on Friday.
He also said he instructed the army chief and air force chief ACM Phanpakdee Pattanakul to stop any military aircraft from Myanmar from intruding into Thai airspace.
"If the conflict in Myanmar spills over into Thailand, that's unacceptable. Military aircraft intrusion into Thai airspace is also unacceptable," he said.
Mr Srettha added that the government has put in place measures to handle an expected influx of Myanmar citizens fleeing the fighting across the border into Thailand.
ACM Phanpakdee said he had asked the Myanmar air force commander to ensure military aircraft from Myanmar do not violate Thai airspace. ACM Phanpakdee added that the Myanmar air force chief is scheduled to visit Thailand next month.
The RTAF's air defence and radar systems have been monitoring Myanmar's aerial operations in Myanmar and have not detected any aerial threat to Thailand's security yet, he said.
ACM Phanpakdee added that he had instructed Wing 4 in Nakhon Sawan's Takhli district to have a squadron of F-16 fighter jets ready for take-off in 15 minutes in case of emergency.
Combat air patrol operations are also conducted along the border and near sensitive areas every day, he said.
Foreign Affairs Minister Parnpree Bahiddha-Nukara on Friday visited Mae Sot district of Tak province, just across the Moei River from Myawaddy, to assess matters after Myanmar's embattled junta lost yet more territory in the latest fighting.
He was accompanied by the National Security Council's secretary-general, Pol Gen Roy Ingkapairote, and representatives of the armed forces.
A stream of people, some fearing air strikes, queued at a border crossing to flee Myanmar on Friday, a day after the strategically vital town of Myawaddy fell to anti-junta resistance forces that are gaining in strength.
The loss of the town robs the junta, already grappling with an economy in free fall, of vital earnings from border trade while strengthening rebel groups such as the Karen National Union (KNU) that led the assault on Myawaddy, analysts say.
Junta spokesperson Zaw Min Tun told Myanmar media some of its troops had surrendered because they were accompanied by their families, and talks with Thailand for their return were in progress.
He did not respond to a telephone call from Reuters to seek comment.
Myanmar has been in turmoil since 2021, when the powerful military deposed an elected civilian government, triggering widespread protests it sought to crush with brutal force.
Simmering anger against the junta turned into a nationwide armed resistance movement that is now increasingly operating in coordination with established ethnic rebel groups to challenge the military across large parts of the nation.
About 200 Myanmar military personnel withdrew on Thursday to a bridge linking to Mae Sot after the KNU said it had taken control of Myawaddy.
But the Myanmar military may still seek to mount a counter-attack, supported by its air force, to regain the town, said Dulyapak Preecharush, an associate professor of Southeast Asian Studies at Bangkok's Thammasat University.
"So there is a question about the possible intensification of fighting in the coming days," he said.
As fighting in Myanmar intensified, the numbers crossing to Mae Sot from Myawaddy doubled this week to about 4,000 a day.
Sanya Phetset, chief of Mae Sot district, said that temporary shelters have been arranged at four local temples for more than 10,000 Myanmar citizens fleeing the fighting.
A sports stadium in Mae Sot has also been prepared as a shelter for Thai evacuees affected by the fighting, he added.
The checkpoint at the 2nd Thai-Myanmar Friendship Bridge in tambon Tha Sai Luad reopened on Friday as lorries and cars stranded on both sides of the border on Thursday were allowed to travel back to their respective countries.
The border checkpoint was closed on Thursday after rebel forces seized the Infantry Battalion 275 garrison in Myawaddy.
The seizure of the garrison prompted about 200 Myanmar troops to flee towards the 2nd Thai-Myanmar Friendship Bridge on the Myanmar side of the border, prompting Thai authorities to close the border.