Just FYI,

Overstay fine for 5 days is 2,500 baht.

Extension fee is 1,900 baht.

Q1. Do I need to prove that the funds came from on overseas source?

-> Funds for a 1-year extension don't require international transfer.

Q2. Is there a minimum balance required in my Thai bank account throughout the year?

-> No minimum balance throughout the year other than seasoning. Your balance can be even zero after you get an extension.

Q. As in, what if I temporarily go below 400k baht at some point during the year, so long as it isn’t within the 3 months before renewal; is this a problem?

-> It wouldn't be an issue. However, better to ask your office along with the application for an extension whether they want you to bring the updated passbook when you go back to the office after the under-consideration period.

90-day reporting window in-person is 15 days in advance until 7 days after the due date, including holidays. It includes the time of "acceptable for you to do late a 90-day report". Sadly, you already missed this period. Now, when you go to the immigration office for a 90-day report in person, they usually charge you 2,000 baht for lack of report. This fine is fixed, and won't be changed if you go tomorrow or months later.

The online reporting window is between 15 days in advance and 7 days in advance of the due date, never been after the due date. If you did today, it would be rejected.

@Ken *****

, There is no "approved" status for TM.30 submission. It's just accepted immediately anyway.

It would be an issue if it passed the "checkout date" on your TM30 receipt when you apply for anything at the local immigration office.

You just update your TM.30. With checkout date filled with longer period or it's open. Some put the date of lease expiry for checkout date field.

Q. Is it possible to do this all online or do I need to visit an Immigration Office?

-> You have to go to the office in person. There is an eExtension service, and you can apply with an extra fee added to the official fee, even though, you have to go to the office in person to get a sticker on your passport on appointment date with eExtension service.

Q. which Immigration Office would you recommend?

-> It's more like depending on from where you go to the office.

Q. can I apply 2 weeks in advance?

-> Yes. The Chiang Mai office accepts extension applications within 45 days of the current stay expiry.

Q. can I make photocopies of passport and take passport photos at the Inmigration Offices?

-> There are copy shops around offices.

@Paul *****

, Unless you travel somewhere after that and you have a receipt, you don't need to re-submit.

It wouldn't be a problem. Just update your TM30 before you go to the immigration office.

It's supposed to be submitted within 24 hours after you arrive at that address, not 24 hrs from entering Thailand.

Not submitting TM.30 violates regulations, but submitting multiple times does not.

There are people who re-submit TM.30 to get a receipt just before going to the immigration office.

No, Australians don't need a visa to stay in Thailand for tourism purposes in the short term.

Visa-exempt entries are still in place but it's 60 days now.

I think you are mixing eVisa and ETA. Check this post, please.

5/

@Ryan *******

, more and more embassies state you need to be in the country until the visa issued, or application could be rejected.