Professor Khoo's academic journey led him to a professorship and the Chair of Malaysian History at the University of Malaya from 1974 to his retirement in 1992. During this period, he was the Head of the History Department and Dean of the Faculty of Arts and Social Sciences. He was the first lecturer outside of Malay Studies to conduct lectures in the national language, serving over 50 years in University of Malaya’s history department and teaching many prominent leaders of the country throughout his career.
Over the years, Professor Khoo has sat on various national committees: the Pardons Board of Wilayah Persekutuan, Member of the National Advisory Council on Culture (1974-1976), Board Member of the Institute of Strategic International Studies (from 1984), Member of the National Human Rights Commission (SUHAKAM) (2004 – 2010), Member of the Malaysia-Indonesia Eminent Persons Group (2008), Member of the Malaysian Anti-Corruption Commission (MACC) (2009 – 2012), Board Member of the Integrity Institute of Malaysia (2004-2013), and the Board of Trustees for Merdeka Award (2007 – 2013).