What are my options for re-entering Thailand after my NON-O marriage visa expires on September 4th?

If you have the money (800k฿) in y'r bank account two months before application, maybe you can considder 'change reason of extension' to retirement. Most of the time you get y'r year extension the same or next day, without consideration period. So, if the money is in for 2 months after 20th of august, you can ask the year extension just after 20th of august (also re-entry permit) 🤷‍♂️

It'd be no harm to ask your local immigration office whether they can extend your under-consideration period if you can prove your travel plan before leaving next week. Whether a new u/c stamp can be until November if you apply for a 1-year extension on or before 4th September, showing your fixed flight tickets (<- means with dates on both ways).

Sometimes they would give you a u/c stamp to cover the period you are out of Thailand if you can show proof of travel out (Tickets without a date wouldn't do the trick).

If they say okay, then you get a re-entry permit and apply for an extension before your current stamp expires. Then get a re-entry permit again when you leave mid-September.

If they say "no, it's too long", then give up the current extension and start over.

Q1. with a Reentry Permit: Can I stay until September 19th (after expiry Sept 4th of my extension of stay)?

-> No, you cannot. Your stay will be until 4th Sep. You might be able to apply for a 60-day family visit extension if you haven't applied for it with the current series of an initial visa and following extensions.

Q2. without a Reentry Permit: Will a get a normal 60 day visa-exemption stay ? (I understand that the extension of stay becomes invalid)

-> Yes, you may.

Remember, no more multiple-entry Non-O visa based on being a member of a Thai family, valid for 1 year on the eVisa system.

If you leave without a re-entry permit this month you will get a 60 day visa exempt stamp when you return. When you return later in the year I'd suggest getting a 90 day Non-O visa based on marriage before travelling as too many visa exempt stamps can be an issue and then you only need to do the extension at immigration (you can no longer get a multi entry Non-O based marriage)

There are no NON-O thai family multiple entries visa available anymore, you can only apply for the single entry

I agree with

@Phil *****

... leave Thailand WITHOUT a re-entry permit and enter Thailand Visa EXEMPT entry...show PROOF of your flight departing Thailand within the 60 days you will be stamped in for on arrival...if questions from Thai Immigration Officer who greets you on arrival.

1. No. You can’t stay past the date on your extension of stay. Re-entry permit just maintains validity of your current extension of stay.

2. Yes more than likely, I would prepare to be thoroughly questioned when re-entering when doing this. The IO officer may show an interest in your plans. As you mentioned you will lose your extension of stay based on marriage and will have to reapply should you want to use a marriage based visa again.

Personally I would enter on a 60-day VISA EXEMPT. If the IO Questions you explain why