Digital nomads are gray areas because number one it’s hard to detect them and number two they don’t take jobs from locals. I am a digital nomad and my employer only hires Americans because it is an American company. I’ve worked for other international companies as a freelancer and the reality is that they only hired people from Canada to US or the UK. The only reason why you need a visa to teach English in Thailand simply because you’re taking money from the economy but as a nomad the origin of your money isn’t the Thai economy