Shanmugha Rajeswara Sethupathi was born to Raja Rajeswara Sethupathi or Muthuramalinga Sethupathi who ruled the estate of Ramnad on 9 November 1909. Shanmugha Rajeswara Sethupathi had an English education and graduated in law. He succeeded to the throne on the death of his father in 1929. As soon as Shanmugha took over the administration of the estate, the land became embroiled in a number of disputes and lengthy court cases. Between 1935 and 1945, the estate was administered by the Court of Wards.
Shanmugha Rajeswara Sethupathi joined politics at an early age. He was elected to the Madras Legislative Council as a candidate of the Justice Party and served as a member of the Madras Legislative Council until 1937 when he lost to Pasumpon Muthuramalingam Thevar of the Indian National Congress. During his period of service with the Justice Party, he served in the Economic Depression Enquiry Committee which enquired into the causes and impact of the Great Depression in Madras Presidency.
Indian National Congress
Shanmugha Rajeswara joined the Indian National Congress in 1946 and was elected again to the Madras Legislative Council as an Indian National Congress candidate. He stood in the 1951 elections from Ramanathapuram assembly constituency and was elected to the Madras Legislative Assembly. He served as the Minister of House Rent Control from 10 April 1952 to 13 September 1953 and as the Minister of Public Works from 13 September 1953 to 31 March 1957.
Other interests
Shanmugha Rajeswara Sethupathi had a passionate liking for horses. He owned a stable of over 50 horses in Calcutta. He also owned an extensive car collection including Rolls Royces and Bentleys. The Raja owned extensive land in different parts of Madras city. Hotel Woodlands is located on the exact spot where the Raja's official residence in the city had earlier stood. The Shanmugha Sethupathi Cup for horse racing has been instituted in his memory. Shanmugha Rajeswara Sethupathi was also a fine cricketer. He played four first class matches during the 1941/42 and 1943/44 seasons for the Madras cricket team scoring 129 runs at an average of 21.50. He also played for the Indians against the Europeans.
Death
Shanmugha Rajeswara Sethupathi died on 4 March 1967 and was succeeded as the titular Raja of Ramnad by his son.