My Non-immigrant O-A multi-entry visa expires on 1 Sept this year, however it will be touch and go whether I get back to Thailand prior to that date.

From reading an earlier post I gather that if I do arrive prior to 1 Sept my visa will be extended for another year. Is that correct? Or do I have to go through a renewal process at a Thai immigration office?

The other thing I was wondering...is it possible to get an extension/renewal through the Thai embassy in Australia?

Thanks for any advice that's available

The visa will get a new one year permitted to stay if you arrive before it expires. You can not extend at a Consulate. So if return will not be before it expires you might want to obtain another such visa, or a single entry O visa for 90 day stay that you can then extend at immigration for retirement one year stays or if you are unable to do either use your visa exempt entry to visit immigration early on and convert to non O visa entry to be followed by retirement extension. Many options but if you can get back before it expires no cost for another year stay (although you will have to buy re-entry permit for any travel).

If September 1st is the enter before date on your visa you will get a new one year entry as long as you do the entry on or before that date. After that date you will need a re-entry permit to keep that last entry valid if you want to travel.

You will not need to apply for an extension of stay until you are near the date that last entry ends.

You can only get a new visa at the embassy in Australia.

If you return prior to the visa expiring you will be given a one year "permission to stay" (the visa is not extended)

It is is important to obtain a re entry permit if you intend traveling during the 2nd year permission of stay.

It is not possible to "renew" a visa and extensions can only be obtained in Thailand.

Your only option assuming you cannot return prior to your visa expiring is to apply for a new visa.

Thanks lopburi3, ubonjoe and nowretired. From your advice it seems best I make every effort to get back before expiry.