Idk, if the number of people executed increases over time, maybe it doesn't.
https://www.afr.com/world/asia/singapore-executions-touch-22...
This article cites Singapore saying the existing laws mostly get low-level users and not kingpins because kingpins operate outside of the country.
https://www.vice.com/en/article/singapore-drug-executions/
Decriminalization of drug use doesn't have to mean decriminalization of anything else. Thieves and murderers should be prosecuted regardless of any state induced by the voluntary ingestion chemicals.