If you're planning on being here for 3 months, get a 60 day tourist visa before you leave. That can be extended one time in country for another 30 days.
Of course you can buy a refundable ticket. You also shouldn't need a plane ticket, just upload your expected travel plans, the US embassies accept a screenshot of the flight you want to take.
Non-OA is a 1 year multiple entry retirement visa that you can only get in your home country. It requires health insurance and 800k baht (the equivalent currency) in a bank account (can be in your home country, Not a thai account).
A Non-O is a 90 day single entry retirement visa. You can get this at any Thai embassy in any country, or inside Thailand. This visa can be extended once inside thailand for 1 year at a time. Non-O does NOT require health insurance, but the 1 year extension does require 800k baht to be in a Thai bank for 60 days before you apply for the visa, and the duration of the time you're in the country.