Depends if you can travel out of Oz and get into Thailand before your visa expires, and that is unknown at the moment. If it looks like you won't make it before the visa expires, get a new one.
You probably won't get a 60 day family extension right now if you have no valid visa or extension to do it with. You will just have to wait and see what happens after July 31st, like everybody else.
Dave you are confusing 2 different extensions.....1. Marriage extension...400k for 2 months before...and usually keep it for a month after to be safe (it has never been 3 months before and 2 after)
2. Retirement extension...800k 3 months before application and 2 months after, mandatory for every renewal. (also min 400k for the other 7 months of the year)
You may be told to leave at the end of the amnesty regardless of where you are a resident. :( They would expect you to return to where you are a citizen :(