We did that when we were on tourist travel and we really had a full thai insurance i even showed them, that didn‘t interested them, so we left without bank account
I think you mixed up your post. Exactly its 2024! If it were 100 years in the past you wouldn't have to do anything. In modern times now, you are not allowed to take to much fluids accross the customs worldwide, you have to leave your fingerprints at immigrations worldwide, they want to know everything about you, accomodation, itinery etc. Some decades in the past all this wasn't necessary at all. So its just bad luck for you that you live in modern times 😉
Is this really an official mail from thai embassy of your country? Somehow „e-visa team“ doesn‘t sound like it. can you follow somehow the senders mail address?
This sign seems to be specifically in front of the government office, the sign with detailed/specific dress codes is in front of every immigration office, thats where most foreigners need to go to. I haven‘t seen the government office since I live here, don‘t know who has to go there.