Resident and retirement visas are complicated and expensive, initially you're best to come on a Non-Immigrant O visa. Try to get a multi-entry. With this visa you can remain in Thailand for 3 months, then you leave the country (easy & cheap to do) and come back in for a further 3 months. With this kind of visa you can go in and out for a total of 15 months, by that time you will have learned a lot more about how the other kinds of visas work.
Foreigners are not allowed to buy land in Thailand, you can buy a condo or flat, you get to own a space but no land. Personally I just recommend renting, prices are cheap, you can move easy when you eventually get driven out of your place of residence by noisy Thais, plus there are a million tricks around to skin a foreigner, so renting is safer until you learn some of the ropes.

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The Truly Wise Man Never Plays Leapfrog With A Unicorn