I can confirm that I have always followed that Jomtien immigration guideline, but during the covid period I still had to queue outside in a crowd for 45 minutes, unlike normal, just walk in, hand in the doc. and go back outside without waiting, regardless of whether others were being treated!
That is why I literally asked the I.O. ( that friendly Indian Thai I.O) what the punishment / consequence / fine would be if I had not done that ......
Clearly surprised and bored he admitted that there was no fine or punishment or consequence regarding this, but that it is meant to help us that we would not act unwisely or forget to keep the obligation to keep the 400,000 in full ..... friendly explanation but a bit of a weak defense, because of course 3 months you have to have 800,000 Baht back in full on the account for the new extension later
So DR jack54 is right .... no forced to do in real
The final controle is by your new extention later if the 800 000 rule was followed in full