After the 1962 Burmese coup d'état, Mahn Nyein Maung became involved in underground political activism.[2] He was arrested in July 1967 and imprisoned in the Coco Islands.[3] He escaped in 1970.[3] He was recaptured and imprisoned until April 1973, under a general amnesty.[2] During his time in jail, he became acquainted with Mahn Aung Kyi, the secretary of the All Burma Karen Organization, who would become his political mentor.[2]
In 2000, he published a memoir entitled Against the Storm, Across the Sea, describing his prison break from Coco Islands in the 1970s, a feat that earned him the nickname "Burma's Papillon."[3] In December 2011, he was sentenced to 17 years in prison for "unlawful association" after being deported by China due to visa issues.[4] In March 2012, he was sentenced to life in prison for participating in acts of war against the ruling government, but was released on 19 March via presidential amnesty.[5][3] Mahn Nyein Maung became an admirer of Thein Sein, who had pardoned him.[6] Mahn Nyein Maung participated in negotiating the landmark Nationwide Ceasefire Agreement, which was signed by KNU on 15 October 2015.[7]
He resigned from the central executive committee of the Karen National Union in July 2020, in order to contest a Pyithu Hluttaw seat in his hometown of Pantanaw, Ayeyarwady Region in the 2020 Myanmar general election, representing the Kayin People's Party.[8] He lost the election, placing third, with 8.83% of the votes.[9] Nyunt Thein, representing the National League for Democracy, won the race with 58.01% of the votes.[9]
He was appointed as a member of the State Administration Council on 2 February 2021, in the aftermath of the 2021 Myanmar coup d'état.[10] Following his appointment, the KNU distanced itself from Mahn Nyein Maung, and reiterated its opposition to the military coup.[11]
