Email them. They are extremely quick at replying to queries online. Generally speaking rental income does count towards the $80k a year passive income requirement for the wealthy pensioner LTR.
Border bounce but be careful. It seems as though you already did at least one border bounce this year. You’re allowed 2 a calendar year (via land border).
UK embassy in Thailand doesn’t provide an affadavit of income so that route won’t work for you. Ask your local immigration office what the requirements are for a 90 day Non O retirement visa. It’s almost certain that you will need 800k baht in a Thai bank account before applying for the visa.
so come in visa exempt. Will give you total of 30 plus 30. As mentioned, you can apply for a non o visa retirement when you get here but be careful, a small number of immigration offices require you do seed the 800k baht for 2 months before you can apply for the visa.