What is the process for someone with an Australian passport to enter Thailand for 90 days, and how can extensions be applied?

Hi members..

Getting bit confusing about entering Thailand from Australia..

Having an Australian Passport does this get stamped for 60 days then apply for 30 day extension.

Or do I have to apply for 60 day E Visa than than apply for another 30 day extension.

I'm planning on spending 90 days in Thailand the doing border hop Nong kai into Laos for a few days then re enter for another 60 days.. is this possible.

Thanks for information