They dont like roofs and their entrances (the crack in front and in the back) need a space of 2m apart (1 normal tile floor); so you can place beehives side by side as long as their front and back are free from walls, rocks, trees or objects in general.

Also the beehives also act like roofs, so placing one above the other (or even above a bed or workbench) will make the game see it as under a roof.