Security cameras had captured images of a Mercedes Benz believed to have been carrying former prime minister Yingluck Shinawatra as it passed a military camp in Sa Kaeo, Deputy Prime Minister Prawit Wongsuwon said on Friday.
The car was not spotted again, he said. The camera did not look beyond the military camp and there was no convoy accompanying the Mercedes.
The regular driver of the Mercedes would be called in for questioning.
Mr Prawit did not say when the car passed the camp.
Gen Prawit admitted he wondered why the Mercedes was not seen again on security footage at the border checkpoint to Cambodia. Officials had been asked which other border passes the car could have used to leave the country.
Gen Prawit had earlier said a Vokswagen and a Mercedes-Benz were in the convoy used in Ms Yingluck's escape.
The former Pheu Thai prime minister failed to turn up at the Supreme Court's Criminal Division for Holders of Political Positions on Aug 25 for judgement in her trial for alleged negligence in failing to prevent corruption and huge losses to the state in her government's rice-pledging scheme.
After her no-show the court issued an arrest warrant, ordering that Ms Yingluck be brought before the court again on Sept 27 to hear its rescheduled ruling.
If convicted she is liable to a prison term of up to 10 years.
