If you have a long term visa eg retirement/marriage and you don’t want your visa to be cancelled when you stamp out you need to purchase a re-entry permit this allows you to come back and your visa is still valid note this will not extend your visa you must return before your visa/extension ends and in time to renew it.
I have never been asked he would just show is flight itinerary if he were, sorry I think this a simple question by the OP was made complicated, I think he’s just coming on holiday and a simple question of are you on a return/round trip could have been asked with the answers of 30 day emption entry.