quit lying. Even if what you say was true concerning monthly income, immigration only accepts Thai bank statements, and without a Thai bank account you could never prove it to immigration. I call BS. You are talking out your ass
Apply for the type O visa before you come to Thailand. As long as you have the equivalent of bt800,000+ in your personal bank account, and a few other details, you get the 90 day visa before you enter Thailand. This gives you the correct visa in order to open a Thai bank account in your name, and then transfer in the bt800,000+ needed when you apply for your one year extension. Without this visa you are going to have a real hard time opening a Thai bank account, and need an agent to do it at a cost of bt6000+ or more. The 90 day visa gives you time to get the money into your Thai bank account,cans have it there for two months before you apply for your one year extension. It is the easiest visa extension to get, requiring the least amount of paperwork. You could hire an agent to do it all, but they cost between bt30,000-bt60,000 each year.
you're in for a rude awakening when you go to immigration and don't have bt800,000+ in your bank account for at least two months before you apply...lolol.
when you get to Thailand if she can produce a copy of the house book she was listed in that will be a big help. At the extreme she might need a DNA test, and be able to compare that test with a Thai relative's DNA test to prove birthright. It helps if she knows which province she was born in, and can get a copy of her birth certificate. Even though her Thai passport is expired, she will still be let in as a Thai, and go through the process of getting her new Thai ID card. It could be simple, based on her expired passport, or involve DNA tests as the extreme requirement. Direct Thai relative's can help greatly.