The Ghadr movement which took birth on the west coast of the United States and Canada in 1913 soon spread to Asian countries, collectively known as the Far East. Thakar Singh was among the first immigrants to join it. He sailed for India at the end of 1914 with the intention of preparing ground for a revolution in the country. Meva Singh, another member of the Ghadr party, who had been chief officer of the French Consular Police at Canton had written a letter to Harchand Singh of Lyallpur commending Thakar Singh to him. This letter was apparently intercepted by government, for on arrival in India Thakar Singh was restricted to his village. No certain evidence coming forth against him he was permitted to go to Hong Kong in May 1915. A letter of his written in November 1915 from Canton and addressed to Giani Bhagvan Singh, granthi or scripturereader at San Francisco and a Ghadr revolutionary, was intercepted. This letter spelt out a plan for a simultaneous outbreak at Ludhiana and Firozpur and for establishing a state in which all property would be held in common, all necessities of the people supplied and all men trained for military service. Doctor Thakar Singh was arrested at Hong Kong and sent to India where he was interned on arrival in October 1915. He was tried at Ludhiana and sentenced to five years' rigorous imprisonment and a heavy fine. Soon after his release in early 1920, he joined the Akah movement for Gurdwara reform. He was arrested on 18 February 1922 for joining a demonstration against the visit of the Prince of Wales and sentenced to three years' imprisonment and fine in lieu of which a major portion of his land was attached.

As he reached Amritsar on 30 December 1924 after his release from the Mianvali jail, Doctor Thakar Singh was honoured with a siropa or robe of honour at Sri Akal Takht. By this time the Jaito morcha or agitation in the princely state of Nabha had come into full swing. The Shiromani Gurdwara Parbandhak Committee and Shiromani Akali Dal had been outlawed. Thakar Singh acted as vice-president of Shiromani Akali Dal from 7 November 1925 to the end of January 1926. He became head of the District Akali Jatha, Ludhiana, on 23 March 1926. By the end of 1926, most of the Akali leaders were released frorn jail and the Gurdwara Reform movement had come to an end. Doctor Thakar Singh retired from active politics and went to live in Rajasthan. He, however, died in his native Ikulaha on 12 August 1945.