Any opinion on kid leashes?

I am showing some friends around Thailand next year. they're bringing their 3 year old son. I think it would be a fine idea to put the little hellion on some kind of leash so he can't get lost or stolen (more about peace of mind for the parents, then a real concern on my part) I know full well that Thais often look at farang as little more than animals, but would a leash just reinforce that attitude, Or is there some other reason it might seem objectionable. If he was a little older it wouldn't be an issue. Any thoughts?