Soysa was arrested in Bombay in July 1943, months after the struggle was crushed, where he was detained for 50 days before being returned to Ceylon, and released on parole.
Following the end of the Second World War he contested the 1st parliamentary election, held between 23 August 1947 and 20 September 1947, in the Colombo South electorate, where he polled third.
[2] Soysa didn't run in the subsequent 1948 by-election, following the dismissal of the sitting member for Colombo South, Reginald Abraham de Mel, which saw the election of Theodore Frederick Jayewardene, representing the United National Party.
Soysa and Jayewardene were re-elected unopposed in 1965, the first time since 1947, when Hameed Hussain Sheikh Ismail was elected uncontested in the Puttalam electorate, that there had been no contest for a seat in the parliament.
He again contest the Colombo West electorate in a by-election held on 21 March 1978, finishing third, losing to Anura Bastian.
Speaking as a minister at the fiftieth anniversary session of the Sri Lanka Association for the Advancement of Science in 1994.