As an actual employee on the payroll, that would be pretty rare. Even when an employer allows 100% remote working, they will not allow that to be carried out abroad for any length of time. Mine certainly didn't. During Covid when I was living in the UK our offices were closed for a year, I was there with my manager's permission, but HR did not know. When HR found out, I was told to return before I hit the 180 days which would have triggered Thai tax residency. In the case you mention above, I imagine he is probably working as an independent contractor, being paid on invoice.