He gained notoriety by becoming one of the highest leaders of the Fatherland and Liberty Nationalist Front, an organization strongly opposed to the government of Salvador Allende through violent means, often resorting to worker riots.

After the 1973 Chilean coup d'état and instalment of the subsequent military junta, he went through a major ideological change, after which he became a political activist, often organizing events against the regime led by Augusto Pinochet, which he accused of abandoning nationalism in favour of global neoliberalism.

[6] Between 1981 and 1982 he was general secretary of the Nationalist People's Movement (Movimiento Nacionalista Popular, MNP), which, in September 1983, was converted into the political party South Wind (Viento Sur).

In October 1982, the MNP was accused of planning a coup d'état against the military dictatorship of Chile, after which Thieme escaped to Argentina.

[7] According to Swedish journalist Anders Leopold, Thieme was responsible for the assassination of Olof Palme,[8] but there has been no solid evidence involving any Chilean citizen in the case.