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