From 1979-1986, the nominee was Chief Legal Counsel of ten (10) big corporations, among which was the Metro Bank, which was the biggest universal bank in the Philippines. In 1986-1990, he was Vice President for Law, Board Director, and Corporate Secretary of Philippine National Oil Co. and Petron Corporation. PNOC was the biggest corporation in the country. In 1990, he founded the ATHENEUM School in Noveleta, Cavite, which is ranked either No. 1, 2, or 3, in the Division of Cavite and among the top schools in Region IV and in the Philippines. Most of Atheneums alumni are admitted by the best universities in the Philippines, where the rate of admission is 2 to 3 for every ten applicants, many of them graduating with honors from the said universities.

Rey is currently a faculty (Professor of Entomology) at UP Los Baños since 1980. He served as Dean of the College of Agriculture and Chancellor of UPLB. He has also served as ex-officio Director of UPLBAA and Director of UPAA for six years representing the UPLB campus.