If you are in Thailand. you are applying for an extension of stay based on being over 50 and not a visa. And if so your money needs to be in a Thai bank.
Now the 60 days visa exempt stamp is automatic. They rarely ask for the 3 proofs unless you have abused the visa exempt system by entering too often. But the money proof is per adult.
You would get a 69 day visa exempt stamp in your passport. This is NOT a visa. Immigration staff can ask you for three proofs (proof of address, Proof of funds - 20.000 thb or equivalent in a major currency per person, and proof of travel out of Thailand within 60 days of your arrival date). But if you are a first time traveller to Thailand you are unlikely to be asked any questions by Immigration. However, many airlines will not allow you to board the aircraft unless you have a returm ticket. Best confirm the requirements with your airline
If your arrivals have all been visa exempt entries then sooner or later the Immigration officer at the arrival airport will declare that you have spent sufficient time in Thailand to show that you are no lomger a tourist and can deny you entry. Maybe it is time for you to obtain a visa appropriate to the reason for your visit to Thailand.