Is it possible to travel to Australia while awaiting a Thai marriage extension before it expires?

Okay most answers covered your situation.

Could you not also:

Instead of applying for the 1yr extension, apply for 60 day visit Thai family extension and get a reentry permit (always).

Then when you return from your trip apply for the 1 yr extension.

It buys you 60 days "in a sort of Limbo" status.

Many use this 60 days to get money in order etc. for the extension.

You can apply on 10th September (1 month b4 expiry). In my experience they won't consider doing it any earlier in Pattaya unless you can show good reason. The consideration period is normally 1 month approx then you should go to pick it up. Again, if you can show good reason, they can amend this period to suit at their discretion.

Alternatively you could consider doing the application at the very end of September b4 travelling abroad in which case the consideration period date would likely be end of October. Obviously you would need a re entry permit, and would need to re enter Thailand by this date stamped on passport. Good luck!

as a general rule you are correct, you can apply for a new yearly extension at most offices when you have 30 days or less left on your current stamp (Some are 45 days or less) and as it is an extension based on marriage you would get the under consideration stamp.

Now what you could do IS when you apply for the year extension talk to the immigration officer and see if you could get a longer under consideration period.

I have seen people show proof they would be out of the country for say a month and get a TWO month under consideration stamp instead. They had to get a re-entry permit that is valid only for that stamp BUT it bought them the time they needed)

An immigration office doesn't have to do that at all and I've only seen it a couple times in real life..

BUT

you're out nothing by going in and talking to them a month or so BEFORE you would apply for your extension (so 2 months early) and see what they say.

Worst they say is no they can't do it, so you'd travel, lose the current yearly extension, start all over from scratch with a 30 day free entry, Non-O and then another year extension

OR

you'd travel, lose the current yearly extension, get a new single entry 90 day Non-O visa from the thai consulate in Australia before you come back and then apply for the year extension after that. . .

Talk to your Immigration about your travel plans and maybe you can apply early