Fwiw, unless it's been changed recently, there isn't anything in mturk's TOS that states that workers cannot use mturk when outside of their country of origin. Iirc, it says something or other like services are not offered to citizens of eligible countries that are residents of another country. I always interpreted that to mean that if you are a US citizen that's living in some country where mturk isn't available, you can't open an account with a foreign address or cash to a foreign bank account just because you're American.
That being said, that doesn't mean that there's no risk in working when outside the country. Amazon's rules aren't clear, their CS sucks, and their enforcement of lots of things is super random. On top of that, I'm sure they do actually care about people selling accounts to workers in ineligible countries, and people who aren't actually taking part in that probably get mistakenly caught up in enforcement.
I was out of the country a lot the last 3 years, and I did a fair amount of work still, but only for a handful of requesters that I had already done work for forever. I didn't consider it to be immoral in any way, but I did consider it to be a small risk.