[3] Thewarapperuma embarked on his political career with the Lanka Sama Samaja Party, serving on the staff of Anil Moonesinghe.

[4] Subsequently, he contested the provincial council elections for the Western Province, representing the Kalutara District, where he secured electoral victory.

As a part of the UNP-led Good Governance administration headed by President Maithripala Sirisena in 2015, Thewarapperuma assumed significant ministerial responsibilities.

[4][6] In the wake of a constitutional crisis in 2018, Thewarapperuma and his cohorts faced temporary removal from their governmental positions under the brief the short-lived Sirisena-Rajapaksa-led government.

[9] Nonetheless, by 2019, he was compelled to resign once more, prompted by the transition to a Sri Lanka Podujana Peramuna (SLPP)-led government following Gotabaya Rajapaksa's election as president.

He rose to fame among people of the entire island especially during the COVID-19 pandemic in Sri Lanka for having provided food, dry rations and other necessities to the rural population of the Kalutara Electoral District.