Code of Criminal Procedure, 1973
(1) Nothing in section 426 or section 427 shall be held to excuse any person from any part of the punishment to which he is liable upon his former or subsequent conviction. (2) When an award of imprisonment in default of payment of a fine is annexed to a substantive sentence of imprisonment and the person undergoing the sentence is after its execution to undergo a further substantive sentence or further substantive sentences of imprisonment, effect shall not be given to the award of imprisonment in default of payment of the fine until the person has undergone the further sentence or sentences.