That sounds reasonable for inpatient, worldwide, renewable. If that is affordable for you, I would take it, as they only get more expensive to start as you get older. Most will have options to include or exclude the USA for anything longer than a few weeks.
, just Google Thailand visa, and you should get a list of the visas. Also, there is an online website (the name escapes me currently) for certain countries' citizens to apply.
You won't be able to become a Thai citizen. Resident, maybe.
You can get long term resident visas. You need to be over 50, have a job there, have a Thai child, or married to a Thai, to start a long-term visa process going.
How many times did you leave Thailand, and how long did you stay out each time? And were you actually travelling around Thailand? They may deem you don't need a Multi entry, and just give you a tourist visa.
They may also determine you are trying to live in Thailand, and suggest you apply for an appropriate visa.