During the war of liberation Moni Singh managed to escape from the Rajshahi prison on 7 April 1971 with the help of common prisoners and joined the War. He was made a member of the advisory council of the mujibnagar government during the War of Liberation.
After the emergence of Bangladesh, Moni Singh was elected the president of Communist Party in the second congress of the party held in 1973. In 1975 he joined the bangladesh krishak sramik awami league(BAKSAL). Moni Singh revived Communist Party in 1976. In the presidential election in 1978, he took part in election campaign in support of Democratic Alliance. In the third Congress of Communist Party held in 1980 he was once again elected president of the party and continued to hold this position till his death on 31 December 1990. His autobiographical work titled Jiban Sangram (2 vols) is an important book on the contemporary politics.