"Applicants applying in Chiang Mai must bring documentation to support residency claims in one of these provinces. Having your house registration from one of the 15 northern provinces is not enough to qualify for a Chiang Mai appointment. "

This is on the US visa site. What exactly SHOULD she bring if house registration isn't enough???

I monitor Consulate Chiang Mai news regularly and have seen this warning before. My guess is to put yourself in the Consulates position and use your best judgment.

It seems to me that if someone shows up with a house registration it proves little. That person could be working and living in BKK but keeps the house registration in Chiang Mai.

I would go in with documentation that shows actual living in the northern provinces such as utility bills, monthly bills such as UBC, foreign originated mail like bank statements from abroad, etc.. Anything that tends to prove your actually living within the jurisdiction of the Chiang Mai consulate should do it.

I monitor Consulate Chiang Mai news regularly and have seen this warning before. My guess is to put yourself in the Consulates position and use your best judgment.

It seems to me that if someone shows up with a house registration it proves little. That person could be working and living in BKK but keeps the house registration in Chiang Mai.

I would go in with documentation that shows actual living in the northern provinces such as utility bills, monthly bills such as UBC, foreign originated mail like bank statements from abroad, etc.. Anything that tends to prove your actually living within the jurisdiction of the Chiang Mai consulate should do it.

What else should she have ready? It's really so unclear on the "official" sites. I've worked under the table for the last 2 years so I'd serve as a horrible sponsor for her. My mother is willing to do it. What does my mother need to do to show she will provide housing / financial support? What should my girlfriend in Thailand bring to the interview? I've heard proof of a house/children/money in the bank. Is the money in the bank a necessity??? She doesn't have much right now and I'm guessing we can't just put a decent sum in her bank account all of a sudden.

Do a search on Thaivisa. There are many threads, many I have posted on, with many suggestions on how to document an application and how to address the primary issue you must prove and that is what are the "compelling reasons she has to return to Thailand"

What else should she have ready? It's really so unclear on the "official" sites. I've worked under the table for the last 2 years so I'd serve as a horrible sponsor for her. My mother is willing to do it. What does my mother need to do to show she will provide housing / financial support? What should my girlfriend in Thailand bring to the interview? I've heard proof of a house/children/money in the bank. Is the money in the bank a necessity??? She doesn't have much right now and I'm guessing we can't just put a decent sum in her bank account all of a sudden.

You or your mother will not be able to 'sponsor' her. She'll have to qualify on her own. However, there is a field on the DS156 that asks "Who will pay for your trip?" and "At what address will you be staying in the US?" You can specify your mother and mother's address if true. No letter is needed but would not hurt.

How Can You Help?

http://bangkok.usembassy.gov/services/visa/NIV%20Help.htm