I watched this video years ago when it first came out...and told both my kids that THIS is what I want for myself. It's do-able on my social security alone, which they would manage. Love that this is an option.
You have a few options at your age. An Ed visa is a possibility. You can also just travel around using tourist visas and explore the area around SE Asia so that you know for certain that Thailand is the spot. I recommend that you open a Thai bank account when you arrive so that you have the option of slowly dumping in "spare change" into that account and build it up. That is what I did and am currently doing. I was on a retirement visa but not yet ready to fully retire, but I do just that (stashing a little cash) and when I return back I'll have plenty of funds to begin the next chapter.
*FYI I do work for a company and earn a reliable income, and they will allow me to live wherever. I doubt I will use the Thailand version of a nomad visa while there.
I find it interesting and amusing that a NOMAD visa for Thailand wants you to NOT be a nomad 555 Seriously!
Nomads usually move around, travel, visit other countries. Thailand wants them to park themselves in Thailand and bring a suitcase full of verified income and documents.
It is far easier to actually be a tourist nomad in Thailand. Come in, stay as long as you can, go somewhere else, come back some other time.