He was elected to the Kerala Legislative Assembly in the General Elections of 1967 from Punalur Constituency and re-elected to the Assembly from Chadayamangalam Constituency in 1971 General Election.
Born in 1955 to Purushothaman and Sulochana at Mullakkara, Chadayamangalam in Kollam district, Ratnakaran became a member in Communist Party of India in 1978.