The LTR would fall under the “retirement visas” category and he did mention “passive income” so he did hear something somewhere. Since the LTR is not mentioned on Thai embassy websites (I think) I decided to mention it . . . plus that is my current visa.
The details about the LTR visa can be found on the Thailand Board of Investment website. Google BOI LTR. It is really passive income required. For example I meet the requirements using my work pension. They also accept certain investment passive incomes but I don’t know the details on that. They don’t consider earned income or savings.
You might want to say where in Thailand you plan to move to since this will help others give their advice. The immigration details can be a little different in each of the provinces.