You apply where you are located because it is e-Visa. If you are in Ho Chi Minh City or any area served by Ho Chi Minh, you apply at the Ho Chi Minh embassy.
It is laughable with the list you presented. It is annoying, arrogance, and trying to assert privileges. No wonder banks rejected it. Pay the agent. Let them make some money also.
Anonymous participant You can ask or you have to do it yourself. You can ask for all the documents you need. I bet when you rent from person x, you have verified 1. the person x owns the property, 2. Person X's ID and you have kept a copy of each document.
If you already have a TM30 attached to your passport, it is a no-brainer at the immigration office. If you don't have one, go to an agent to get a residence certificate.
They are not obligated to answer correctly every question foreigners ask. Thailand is allowing foreigners to live a decent life in the country that one cannot get in his home country. What more do you want? It is not a privilege.