IRL bee apiaries can be as little as 6 inches apart but no one does that. You need room for movement and equipment between the apiaries and you also want to keep your hives from fighting and stealing each other's honey when there aren't enough nectar producing plants in the area (due to say a drought) and to keep them from spreading pathogens from one apiary to another.

If you put your bees in an open area inside your base they have to be half the distance away from the wall's height for the bees to be happy and the full distance of the walls' height if they are in a corner and the entrance to the hive has to be facing away from the walls. If you separate them by a 1 meter tile's worth of space you can walk between them and they will be happy.

You can also put them inside a roofed building as long as the hives are far enough away from the wall and you use smoke holes or cheese the roof height the way you can with venting smoke. The hives will say the bees are unhappy but they will still produce.