you can mark individual workers using marking numbers (different colors for different colonies) and use cameras to monitor bees entering the individual beehives and to monitor the inside of the hives.
If you want to prevent robbing you can equip your hives with robbing screens and reduce the size of the entrances. You should also try to separate them at least a few meters from each other.
Usually robbing results in fights at the entrance of the hive and in a large pile of pieces of wax on the bottom board or at the entrance. This wax comes from the honey being uncapped by the robbers.