Why do you want DTV your GF? Can't she apply for herself? Does she not have 500K baht? If she does not have the money, I will urge her to save up the money first before applying for a DTV. DTV is not going away soon. Or else, you can marry her and apply based on the marriage.
I read a guy (a US citizen) got his DTV while residing in Ukraine, and he applied from Ukraine to his Thai consulate in the US. A US driver license can always be used for your permanent address in the US for EVISA applications in Thai embassies/consulates.
Anonymous participant loop hole is to form your own company and give yourself some income. or create client (members of your extended family, preferably different last names) contracts documents and Tell them to send you some money that you had given to them earlier.
Just get a Non-O based on family visit. If possible, get a multiple entry Non-O; if not, get a single entry Non-O. You can also get a 60-day extension of your non-O. If you have 400K Baht in Thai bank, you can also get a one year extension. You can also spend the money immediately after getting your extension, unlike the retirement extension. So many options are available to you.
Hopefully, you get it before that. Otherwise, you can come to Thailand, and when it arrives in the email, just do a border bounce, and make sure when you enter, tell them that you have a DTV.
Do you understand what a multiple entry visa means? If not, please educate yourself about visas. I can provide the answer, but it will keep you really uneducated about visas.