Thailand still suffers from hard drugs abuse, including opiates. Singapore is a very tiny city-state with a massively repressive government. Not really good benchmarks/role models. Even in Singapore you can find drugs, it's just absolutely stupid to do it if you are a tourist given how draconian drug laws are there.

On the other hand, countries like the Netherlands and Portugal figured out a way for drug users to not die. That's probably the first thing you should fix: how to help people to not die when using drugs. Educate your population about it, most Dutch people I know are very aware of drugs; their effects, risks, etc.

The cat's out of the box, there's only one level of repression that could have a chance to work on stopping the flow of drugs: maximum repression by the government, maximum shame by the population, is that really what you want? I don't believe that's a solution if you are already in a free society...