
Visit, who ran the GPF for eight years, said he submitted his resignation to the fund's board yesterday to show responsibility.
But he said he never intended to damage the organisation and that he might have "committed an honest mistake".
Earlier, the Public Sector Anti-Cor-ruption Commission (PSACC) said Visit should face disciplinary action and ultimately be held criminally responsible for his questionable decisions regarding the GPF's stock investments, allegedly using inside information.
PSACC secretary-general Tharit Phengdit said his agency's initial finding was that Visit broke the law on two counts: by using inside information for stock investments; and then, in violation of the Criminal Code, deliberately damaging state authority.
An internal GPF investigation found Visit had merely breached professional ethics with decisions that caused huge losses to GPF investments on the Stock Exchange of Thailand (SET).
Visit has thus far denied any wrongdoing, while the Democrat-ruled government has applied political pressure to remove him.
Visit said it was up to the board whether to investigate him.
Pakorn Malakul Na Ayudhya has been appointed as chairman of an investigative committee probing Visit's actions.
He said the committee would meet for the first time on Friday to gather evidence from Securities and Exchange Commission, SET and GPF lawyers.
After the investigation, the committee will give Visit an opportunity to testify, either orally or in writing.