No need to explain anything. This is a professional relationship, not a personal one. "I have left X and relocated to Asia to pursue new challenges. I now work

No need to explain anything. This is a professional relationship, not a personal one. "I have left X and relocated to Asia to pursue new challenges. I now work as a freelance contractor." is fine, hell, it even sounds exotic! Who wouldn't want to work remotely from a foreign country? Keep the bad out of your sale pitch. They don't need to know why you have moved and neither do they need to know that you are currently not employed as an engineer.