Can I Apply for an O-A Visa Extension from Within Thailand and Use Local Funds?

And show other document, like rental agreement, owners ID, house book, photo of yourself outside and inside your house, but every immigration office is different so it’s better to ask for a list of what they require

And if you are extending the OA inside Thailand...you will need proof of health insurance which meets requirements.

You can apply for the 1 year Extension of Stay based on being over 50 years of age. If you use the banked money it must be in an Thai bank account on your name for at least 2 months prior the application date and must stay there for at least 3 months after and the rest of the year not less then 400.000 Thb.

Not sure what you mean by able to return, but according your Embassy website there are regular flights available.