One recent statement with the 500k has been suffice to get approvals. Can be asked to provide more statements so maybe best to add several more to avoid a delay.
The OP is not asking about an extension, he is asking about what he needs to retire in Thailand. You can see others have given him advice about how to get a retirement visa. The application for the retirement options is via the Thai embassy website. Making an extension in Thailand is totally different which is why i never mentioned it.
Houses are sold online nowadays, properties managed online too along with receipt of rents. Landlords, real estate investors have gained DTVS from the London Embassy. If they show how they work online, should not be a problem getting one in NY.