You would register your marriage at the local amphur office. If you have been married before, you will documents from Australia showing you are legally divorced. You will need a certified copy of these and a certified copy of your passport, ith of which you would get from your embassy here in Thailand. Once married, you can the apply for your Non-O, and you will need to have ฿400,000 in your thai bank account. If you dont have a thai bank account, that is where you will run into difficulty. Good luck