You need an embassy visa for Brunei if you have an Australian passport
Visa options for Brunei
Visa on arrival for a maximum of 30 days for Tourism
Travelers need a visa to visit Brunei for Tourism for more than 30 days. Travelers do not need a visa if staying for 30 days or less. Travelers can get a visa on arrival in Brunei at the port of entry, such as an international airport or border crossing.