Hello.
Adhd/ADD is quite common and often missed or overlooked by parents as children being “naughty”. It is good that you are looking into it.
However, for a proper diagnosis, certain criteria need to be met with and only a trained specialist can do that.
Meanwhile, you can make a symptoms list of what you have found worrisome in his behaviour.
Next Steps
See a psychiatrist who will decide whether it’s ADHD or any other reasons for lack of concentration