Try making the consequence more related to the thing he needs to do, ie if it's unstacking the dishwasher, don't serve dinner until the plates are unstacked to eat from. If it's folding laundry, let him run out of clothes completely...etc. He'll soon learn the value of what needs to be done.

BTW you are not alone, I have a highly distractable 9 yo DD, we *still* get the timer out for some tasks otherwise she just wanders off to la la land and 45 mins you're still waiting!