"To drive in Thailand, you need to have a current Australian licence. There are some rental car agencies that will require an International Driving Permit (IDP) to sign with the agreement, according to the Australian Embassy, Thailand. Though it is not a licence itself, this will act as proof of validation of your Australian drivers’ licence"
So some rental companies want an IDP
https://www.travelinsurancedirect.com.au/blog/need-know-driving-thailand
This is from an insurance company