Prasong started his civil service as a teacher at Ratchaburi boarding school later transferred to military service at the Directorate of Intelligence, Royal Thai Air Force to the rank of a Pilot Officer. He was a close confidant following
Siddhi Savetsila to the Air Force Security Bureau. From then in 1966, he received a scholarship to study intelligence at the
United States Air Force. Upon returning, he moved to the Office of the
National Security Council and in 1980, was the Secretary-General of the National Security Council, following the retirement of Siddhi Savetsila. In 1986, he resigned from the Secretary-General of the National Security Council, to be Secretary-General to the Prime Minister
Prem Tinsulanonda. His image of the will of the
intelligence expert resulting in the nickname of "
CIA of Thailand" and got another nickname, "Co-Prime Minister" from Prem's secretary-general. ==Critics==