The Asset Examination Committee (AEC), set up after Thaksin was ousted in a bloodless coup last year, will ask the central bank to provide details of his money outflows and the British government to help verify the takeover.
"We want to know if Thaksin really bought the club. If so, where did he get the money from and whether that money had been declared with the Counter Corruption Commission," as required by law, AEC chairman Nam Yimyam told reporters.
Another AEC member, who declined to be identified, said the panel would ask the British Embassy in Bangkok to help find out whether the takeover was done by Thaksin himself or by nominees and how it was financed.
"If the probe shows he actually bought the club, we then will have to find out whether the money came from stock manipulation or legitimate businesses," the AEC member said.
Thaksin's family cemented their control of Manchester City in July when they took ownership of 75 percent of the shares in the club for £81m.