If a harmless snake is visiting the hens' nests and helping itself to an occasional egg, I say let the critter be. An egg or two ain't no big deal. Many snakes are beneficial, and they like to eat, same as you. If, on the other hand, so many eggs are stolen that it's cutting into your profits, or if the thief is venomous, you can try this very old solution: Glass eggs.
Eggs made of thin glass were used quite often by chicken farmers of the twentieth century. The eggs were placed in nests to induce hens to start 'setting'. An added benefit was that the eggs worked as a snake 'deterrent'. The glass egg is placed in a nest known to be frequented by a snake. As nature dictates, the snake will swallow the egg, whole. It then wraps itself around a fence rail or tree limb to break the egg.
I'll spare you the details, but I've heard accounts from old timers who noticed a glass egg missing, only to later see a dead snake wrapped around the railing of a pasture fence. Good bye, Copperhead!