As you're travelling in a camper van the only way to do the 90 day report at your location, is to book into a hotel for 1 night and get a copy of the TM30 they should file. Other than that, just report late when you get back home and take the 2000 baht fine.
I had 7 approved applications up to Feb 2024, then for no reason I've had 8 rejected since then and none approved, the latest being yesterday but I've also reapplied so I'll see how that goes. I know I input the correct data, I've been within the application window so I'm at a loss as to why they get rejected. 🤔🤷♂️ On the plus side, it takes me 15mins to go to the drive through and it's done in 2 minutes.
... you can tell me whatever you like but a medical extension is possible but, as you mention, it would not be a great idea to actually plan around getting one.
... Some medical procedures prohibit flying/travel so the OP could certainly get a medical extension for recovery, until such time the doctor cleared him to fly.
The under consideration time can vary, my last one was 5 weeks and I've had 6 weeks in the past so whatever date they stamp in your passport will be the date you need to return to get the extension stamp.
The statement and bank letter are usually good for 7 days but the bank book must be updated on the day.
In Chiang Mai I go to the bank the day before and get the statement & letter and the following morning around 7am, I go to the ATM/PUM, withdraw a small amount, update the book in the PUM then go to the IO and get a queue number nice and early, wait for the photocopy office to open and photocopy the last (updated) page in my bankbook and rejoin the queue for document checking ... easy!