First stay will be 60 days, second with extension.
That doesn’t look like you try to stay long term bc of the missing extension on the first stay. And I haven’t heard of ppl having problems with 2 extended stays. Only at the third entry after a short stay outside.
And if you’re staying as a tourist anyway, you can go to another province if the first try is denied.
Homepage of the embassy in Paris is the one you need to read.
That said…
Get a NonO visa (OA needs a health insurance which you will probably replace later) or at least a tourist visa.
Open an account and put 800k in it (must be transferred so that it says foreign in a statement later!) and never touch it again.
Or
Assert that you will be able to transfer
*****
every single month to that thai bank account even if the euro looses 50% of its value.
I’m doing the 800k because I missed the 65k one month on my first try and had to restart (going back out of the country).
About 2 weeks before end of your visa go to the immigration and get your retirement extension. They will need a statement and certification from your bank and other papers.
There are other ways but those are the simple and sure paths to follow.
The immigration of your province will answer all questions (this is Thailand and nothing is written in stone)
If that is approved, you’re good, because the retirement extension (or LTR or whatever you want to get) are done within the country. Nobody will ever know about what happened before.