quoopy, Welcome to Physics Forums!
Your question is "right up my alley". I am a retired Senior Field Engineer. I have lived and worked in twelve different countries totaling more than thirty years. Also I have visited more than sixty-five countries. (A friend of mine calls me a "compulsive note-taker" because I have a list of over three-hundred fifty commercial flights I’ve taken.)
Nearly all of this international living and work was as a Field Engineer for some company on a "service or support contract" supporting the customer using my company's product(s). Most were for defense-related products (radars, missiles, and sonar), so my customers were usually foreign military; in my case, usually Air Forces and Navies. I have also served in this capacity with the USN, USMC, and USAF. The common term for this job is “tech rep”.
So, if you are serious about doing this kind of work, I suggest you do your homework: research and identify those companies that produce complex systems that require on-site factory support and that export those systems to foreign nations. You will be expected to learn every aspect of installation, operation, and maintenance of the system. As the on-site representative you are responsible for giving formal training courses, providing constant on-the-job-training, recommending modifications, installing approved modifications, giving feedback to correct errors in technical manuals, and being the liaison between all customer support issues and your company's engineering department.
Personally you need to be adaptable and flexible. When you live in another culture you give up your familiar comforts and friends. You must learn how to get your personal needs satisfied within the cultural limitations. Your position is partly an ambassador from our country, so your behavior is always on display. It is not your job to evaluate the customs of another culture. Even if you personally disagree with a social norm, for example, the treatment of women, it is not for you to judge the correctness of native customs.
If you do your company research properly you may even select the product you’d like to work with. Then you may walk into the interview and simply say, "Here I am, ready to contribute my services "in the field" for the company's profit." Good luck.
p.s.: aircraft manufacturers always need Field Engineers