Fugitive sibling former prime ministers, Thaksin Shinawatra and Yingluck Shinawatra, have left China and are bound for Japan, according to deputy premier Prawit Wongsuwon.
Gen Prawit's remarks came after a photo of the pair emerged online on Saturday with reports suggesting they were in Beijing.
The deputy premier said relevant agencies will work on bringing them to justice. He said the two former premiers were heading for Japan after China.
Prime Minister Prayut Chan-o-cha, meanwhile, shrugged off speculation the pair's presence in China could create political instability in Thailand.
"I have no opinion about that. This is a matter of a foreign country and relevant agencies which are keeping track of them," Gen Prayut said.
Asked whether it is coincidental that the photo emerged when an anti-coup protest was being staged at the same time at the Democracy Monument on Saturday, the prime minister said: "I don't take any interest in it. Do not pay attention to it. Why are you interested in people who break the law?"
- Earlier report: Yingluck chase switches to Beijing
Gen Prayut was speaking Monday after attending an event to mark International Human Rights Day at Government House.
Speaking at the event, Gen Prayut said people still lack a clear understanding of human rights, where laws and the constitution are inviolable.
"However, for Thailand, there are still two people committing activities overseas, which cause turmoil for people in the country," said the prime minister.
Anyone who commits wrongdoing must enter the judicial process, he said.
In his speech at the event, Gen Prayut said any foreign offenders who break laws in Thailand are arrested and extradited to their home countries, and every country must respect the rules.
Meanwhile, Foreign Minister Don Pramudwinai said he was informed that Yingluck was in Beijing.
Her Thai passports were cancelled, but Ms Yingluck may have obtained a passport from another country in exchange for investing in it.
He said the ministry had notified various countries about Yingluck's fugitive status.
Yingluck fled Thailand last August to escape punishment over her administration's failed rice-pledging scheme, just as the Supreme Court's Criminal Division for Holders of Political Positions was set to deliver its ruling. She was sentenced in absentia to five years in prison.
Deputy police chief Srivara Ransibrahmanakul said he instructed the Royal Thai Police's Foreign Affairs Division to write to Interpol and asked the Foreign Ministry to trace Thaksin and his sister based on information about their transport routes, airlines they took or what their destinations were.
Forensic officials were also ordered to examine whether the photo of Thaksin and Yingluck was genuine, Pol Gen Srivara said.
Meanwhile, the Pheu Thai Party has denied it is finding a replacement for its acting leader Pol Lt Gen Viroj Pao-in, according to Phumtham Wechayachai, the party's acting secretary-general.
Mr Phumtham described as inaccurate news reports that the party's three former prime ministers -- Thaksin, Yingluck and Somchai Wongsawat -- had met overseas to discuss replacing Pol Lt Gen Viroj.
As far as he knew, the three former premiers have not met or have scheduled a meeting to discuss the issue.
Pol Lt Gen Viroj was carrying out his duty legally as party leader.
The Pheu Thai Party also has no reason or justification to switch leaders at this time, he said.
Also, the ban on political activities remains in effect which bars parties from meeting to pass decisions on important issues including selecting a party leader.