Why did you apply for DTV while you still have a valid visa to enter the country. With METV valid till end of October you can stay 60 days when entering before it expires and then extend for another 30 days, that means somewhere in January next year.
If you are over 50, you can get a retirement visa, and in that case you can transfer the income of the annuity monthly to Thailand where it can count as income, so yes they like people that are not reliant on any employer, you can get a better, but less flexible visa than DTV in that case.
I am also coming from (Western) Europe, but I feel ashamed when I hear thinking fellow West Europeans this way.
As foreigner you are visiting a country and just are a guests who should behave as a guest and respect local traditions and culture, just as we in Western Europa also expect foreigners to respect our traditions.
You pretend to be wealthy, rich and important, behave like a snob, but in the meantime you present a poor man visa like DTV, no wonder the IO is having the attitude you describe.
You seem to be stubborn and don't want to believe me. I don't know where you got the incorrect info from or if you think you don't have to leave Thailand in 5 years, but DTV just does not allow that, meaning EACH 180 days new stamp again has to be followed at day 90 with a TM47 report in person.
Which subsequents? Only when you do an in country extension, ther will be a 2nd and 3rd one and when you plan poor even a 4th, but most DTV holders do a border bounce and that would mean if the do their first report not before 90 days, there never will be a second one.