Let the post know your travel plans and when you're leaving the country. We suggest you find out about this before you enter the country. If you are required to register, do so. You may need to maintain contact. When you land in another country, its laws apply to you.
Ignorance is no defence.
You remain subject to relevant Australian laws as well. In some countries, drug offences carry the death penalty or life imprisonment and flogging. Don't assume 'soft' drugs carry milder penalties. Penalties for marijuana and alcohol can be severe. Be aware that medicine sold over the counter in Australia may be illegal in other countries.