He also served as the Governor of Punjab and Andhra Pradesh.He was considered a central figure in Kerala politics.

Under the influence of his mentor A. Narayana Pillai, he was attracted towards the newly formed Travancore State Congress and he abandoned full-time practice in favour of agitating for responsible government.

Parur T. K. Narayana Pillai was unanimously elected the leader of the Congress Legislature Party and he assumed charge as the first chief minister of Travancore-Cochin from 1 July 1949.

By that time Thanu Pillai left Indian National Congress and joined Praja Socialist Party (PSP).

He resigned on 10 February 1955 and was succeeded by Panampilly Govinda Menon as the last Chief Minister of Travancore-Cochin.

The Communist government was dismissed on 31 July 1959 and President's rule was imposed in the state under Article 356 of the constitution.

Fresh elections were held in 1960 and Thanu Pillai became the second Chief Minister of Kerala, as head of a PSP-INC-Muslim League coalition administration.

[1] Two years after resigning as Governor of Andhra Pradesh, Pattom Thanu Pillai died on 27 July 1970, aged 85 at his home in Thiruvananthapuram.