citizensinformation.ie/en/go … _vote.html
"You must be registered at one address only and you must live at that address on 1 September before the register comes into force. If you live away from the address at which you are registered, you will need to contact the registration authority and give them your new address.If you leave your address but you plan to return there within 18 months, you can continue to be registered there, as long you do not register at any other address.
If you are an Irish citizen living abroad you cannot be entered on the Register of Electors. This means that you cannot vote in an election or referendum here in Ireland. (The only exception to this is in the case of Irish officials on duty abroad (and their spouses) who may register on the postal voters list). "