I am in agreement with Ashwini Sir. The rationale behind the said case of the Calcutta High Court (read: Soma Saha Sen Vs State of West Bengal) is that Right to Trade is a fundamental right as enshrined in Chapter III under Article 19(1)(g) of the Constitution of India and the same does not stand eclipsed by the continuing incarceration of a prisoner. The right in Art. 19(1)(g) can be abrogated only in special circumstances as mentioned in Art. 19(6).
Furthermore, it is advisable to look into the State's Jail Code for information regarding the enjoyment of rights by the prisoners and if any disqualification exists there.
Link of the case law mentioned- https://indiankanoon.org/doc/35871235/