, I have faced this claim of "misuse" myself at Poi Pet border station. They said I should go get an extension instead, that the Non-O 1 year visa should not be used for getting long term stay in the country.
, ok, if you are sure. I am asking because there have been talks about removing the multiple Non-O at all as at least some border stations consider it a misuse of the Non-O visa.
Any income that can be documented should be fine. Either documented by a) the affidavit method where your Embassy certifies your monthly income (most embassies won't do this), or b) the legalization method where your Embassy legalizes documentation of income from the sources of income (however some Immigrations won't accept this method).
, yes, there was a story about how many millions collected every year stored in a warehouse used for nothing but "nice to have if some foreigner committed a crime in Thailand". Gives new meaning to the "needle in a haystack" expression 🙂
, as for Covid there is only a rule about proof of Covid vaccination (two shots) or proof of PCR-test no more than 72 hours before departure. More generally, IMM might ask for a hotel booking for the first night and money in cash (I think 10k THB for one and 20k THB for family) but they rarely ask for it, but you must fill in an address on the arrival card for your stay.