Singapore is more aggressive about finding crime, catching criminals, and has a lower bar for what is considered a crime. Those would also affect their crime rate.
That’s common rhetoric. If something is good in the US, it is because of democracy. If something is bad in Singapore, it is because of totalitarianism. If something is bad in the US or good in Singapore, it is because of their specific “non-political” policies.
And that end justifies any means, right?
Jumping in front of a train also has the death penalty; drug dealing in Singapore is just another form of suicide.