[2] Pillay was born on 3 April 1905 to Kolappa Pillay and Parvathi, a Tamil-speaking couple in the village of Aloor in the Kalkulam taluk in the Southern division of Travancore state (presently in Kanyakumari district of Tamil Nadu).
He was educated at the English High School at Kottar and the Scott Christian College in Nagercoil.
In 1948, Pillay obtained a doctorate from the University of Oxford for his thesis on "Local Self-Government in Madras Presidency, 1850-1919".
In 1966, Pillay was made head of the newly created Department of Social Sciencies and Area Studies, a position he held till 1971.
In 1972, Pillay succeeded K. A. Nilakanta Sastri as the Director of UNESCO's Institute of Traditional Cultures of South East Asia.