A voracious reader and prolific writer till his last days, Pillai has been the intellectual face of the CPM in Kerala for several decades. Known as PG in political circles, the Marxian thinker had been the chief editor of CPM mouthpiece Deshabhimani from 1964 to 1983. Along with E M S Namboothirpad, Pillai rejuvenated progressive thoughts in Kerala.
He was attracted to the Communist movement when he was jailed during the freedom struggle. In 1953, he became the youngest member of state committee of the undivided Communist Party. He had been a member of the Thiru-Kochi assembly before the formation of Kerala in 1951. During 1954-55, he also worked in the party in Delhi.
After the party split, Pillai stood with CPM. Later, he got elected to the Kerala Assembly — in 1957, 1964 and 1967. Pillai had faced disciplinary action in the party. In 2003, he was sacked from the state committee on charges of making outrageous comments on EMS.