There is no short-term extension for Non-immigrant type visas and extensions.

If you haven't applied for a 60-day family visit extension with your current series of initial visa and following extensions, you can apply for it at the local immigration office by showing proof of relationship with a Thai wife.

If you have already applied for it with your current stay, you have no choice but to leave within the current stamp and enter Thailand again to avoid overstay.

Did you check the information from RTE Berlin and try to contact them directly?

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.

@Peter *********

, same. Nothing is different regarding the entry stamp on the re-entry permit, between single and multiple re-entry permit.

Please contact your immigration office for details as it is office specific condition. Most offices accept yearly extension application 30 days in advance until the due date. Some offices such as Bangkok, Chiang Mai, etc, accept those from 45 days before the due date.

The yellow house book and/or pink ID card have no bearing on your 90-day report. The immigration office where you submit your 90-day report is the one to which you submit your latest TM.30.

@Andrew ********

, it is applicable for anyone who wants to use the banked money method for an initial in-country Non-O retirement visa at Jomtien.

You report 90 days to the immigration office where you have your latest TM.30.

Remember, some offices may not accept online reporting if you have newly moved to that province until you apply for an extension there.

Entry stamp on Single or Multiple Entry Tourist Visa is always 60 days with possibility of one 30-day extension per each entry of 60 days. No difference on the maximum length of per stay.

@Udomsil *********

, Don't forget to tell to the officer about your travel plan during under-consideration period when you apply for an extension. There is a chance the officer(s) may contact applicant during u/c. If you skip the contact, you might get a risk to lose the application.