Can I use my monthly Social Security and savings to meet the financial requirements for a Thailand retirement visa?

It depends where you apply and the type of retirement visa you apply for. If you apply for a Non-OA visa in your home country you can use funds in your home country but will need insurance. If you apply for a 90 day Non-O visa in your home country you can use funds in your home country but will need 800k baht in a Thai bank to extend beyond the 90 days (needs to be in bank for 2 months before applying).

If you apply inside Thailand for a 90 day Non-O visa you must have 800k baht in a Thai bank which you'll need to keep there for your extension.

Funds for extensions need to be in the bank 2 months before applying, kept there for 3 months after and never go below 400k baht for the year.

Thailand is a hassle to stay long, Laos is much easier, but not as beautiful as a whole, although there’s plenty of nice places here

No can do.

For your first year of a Non-O (over 50) you have to do the 800k in a Thai bank method unless you get a Non-OA. After that for subsequent extensions some Immigration Offices allow the split method, you'd have to ask them locally what they allow.