@Raquel *******
Sales is a bit vague. The Thais do not want foreigners doing work that a Thai could do. I do not have a saved link as I am not in the job market but there is a list of allowed and not allowed jobs on the net. In a pre Covid time you would enter Thailand on something like a tourist visa, find an employer who will prepare all the paperwork for you to get a work permit and you would go to a nearby country to get a Non O B visa. In Covid times with closed borders you would basically get everything done before leaving home. VAnither thing to think about is depending what you plan to sell, and to whom, the languages barrier can be a big issue. I say languages as there are enough regional dialects that can really mess you up even if you know central Thai.