It is NOT an actual resident visa. It is more of a glorified tourist visa - to use your terms. People will use it as a means to stay up to almost 6 years like they were residents, though. The rest is between you and your countries consulate. I didn't know there were countries that refuse applying for a new visa through their consulates abroad when on "the wrong" kind of visa. Where are you from? Learned something new. German consulates for example (and your name happens to sound German), have different prices for obtaining a new passport abroad: the regular price for true residents abroad, and a significantly higher price for the "glorified tourist" category.
Obtaining the visa with a contract stating that you are free to work remotely (from Thailand) should likely work. But only the Thai embassy in the UK can definitely answer that. Question is: What will you live off of after those 6 months? There is a chance that at every extension of stay or every new entry into Thailand, that people would have to demonstrate that they still fulfill the underlying requirements (i.e. still having a remote source of income).
Sadly this is “normal”. Prices vary drastically between different consulates. As with everything in Thailand … nothing is ever coherent between different offices of the same organization. Same with local immigration offices. And then they wonder why people try to play the system and shop for the more favorable consulates and immigration offices.
In theory: yes. In fact, the respective Thai law (the Thai Immigration Act of 1979) does not contain any hard limit on how many times or how much time per year one can spend on a tourist visa or visa exempt. That does not mean, however, that immigration officers will actually let you in unlimited and indefinitely. At some point, they will assume that you are not a tourist anymore and that you either don't have sufficient funds (Section 12.2) and / or that you must be working illegally while in Thailand (Section 12.3). Of course that is an unproven stretch at that point, but your options to appeal are limited and lengthy. Thus in effect, there is some sort of soft limitation and people have been stopped and sent back.