If it’s a legit self employed business and you pay tax then I can’t imagine it would be too different to say a freelance web designer or similar. Would need to show work contracts, registered company, tax proofs etc.
Not recently, but I applied at London for remote worker and processing was very thorough and the proofs requested were extensive. It was no easy task. Though if requirements are met it should pay dividend.
It’s nice that you wrote your experience down though, always feel free to reach out to people for help. Some DTV holders have been remote workers in Thailand many years and could pass on valuable info so you do not become ensnared / have a negative experience.