That's true: Drones fly as far as 15-16 miles away.
There are multiple options:
1) Mark every newborn drone;
2) At start in the season use a queenseparator at the bodem: other drones can not enter the hive. Then, you need to build a flying cage (where drones cannot escape) for above of the hive (use f.e. a queen separator at one side of the cage: the bees can fly out buyt the drones can't). Every day (after the born of the drone), you can let them fly in the cage.