I would just like to correct a common misunderstanding of this term.
Snakes are venomous not poisonous. Venom is injected and poison is absorbed (through skin or digestion).
Relocating wild animals too far away from their home range is a death sentence by starvation and/or dehydration. If you insist on moving it 5-10 miles away, it would be best to euthanize the snake. Just my opinion based on the welfare of the snake who happened to wander onto your property.
it could kill your hen if it is as big around as a dime or nickel (even though it couldn't eat her) si center she would defend her nest against it and it would try to defend itself against the hen.
I would definitely move it about 1/2 or 1 mile from where your hen is
Do you have a body of water near you? How big is it? Do you have a picture? I'm not an advocate of killing snakes. I'd rather have snakes and spiders around than the vermin and pests they control.