A senior police officer has told investigators he was "ordered" to help former prime minister Yingluck Shinawatra leave the country, according to Deputy Prime Minister Prawit Wongsuwon.
He said the man has also given authorities the name of a person behind the great escape, but the deputy prime minister would not divulge it.
Investigators began interrogating three police officers, one a deputy commander, on Thursday night about Ms Yingluk's rapid departure.
The questioning was led by deputy national chief Pol Gen Srivara Ransibrahmanakul, who later relayed the results to Gen Prawit.
"The deputy commander said he had received an order from another person and gave the name to interrogators," the deputy prime minister said. "The person is in the country but I cannot give you more details," he told reporters.
When asked, Gen Prawit refused to say whether the mastermind was a former Metropolitan Police Bureau chief.
National police chief Pol Gen Chakthip Chaijinda said a special disciplinary panel was being formed to look into the actions of the three police officers. (continues below).
Police on Thursday night also seized a Toyota Camry with the plates chor khor 5323 believed to have been used to take Ms Yingluck to the border. The vehicle was left near a house in Nakhon Pathom’s Muang district.
The sedan was one of the vehicles used in the operation and Ms Yingluck fled with her secretary, the deputy prime minister said.
Gen Prawit did not give details about the three police officers under questioning, only saying they work for Provincial Police Region 5 and the Nakhon Pathom Provincial Office.
He also would not say whether the three officers admitted Ms Yingluck made her escape through Sa Kaeo, citing the sensitivity of diplomatic relations.
But he previously said on Sept 12 that at least two cars were used in the plot and the former prime minister went out through the eastern province.
Ms Yingluck is wanted on an arrest warrant issued by the Supreme Court's Criminal Division for Holders of Political Positions after she failed to show up for the ruling in her rice-pledging case trial on Aug 25. The court confiscated her 30 million baht surety and rescheduled the delivery of its judgement for Wednesday next week.