See Malawi : https://en.wikipedia.org/wiki/Gambling_age#Africa
See Afganistan: https://en.wikipedia.org/wiki/Gambling_age#Asia
I doubt those legal age are really enforced that much in many countries. My first public gambling (prefer to call it betting) was at a very young age in a church compound (probably during something called bazaar or something) yet it was allowed back then. The games were appropriate for kids though and probably traditional.
Many of us likely bet as kids especially in our homes. I guess the problem is indulgence, which is gambling, if it doesn't benefit the kids positively. Kids spending lots of time (without spending money) on nonbeneficial games could be termed as gambling aswell.