@Stephen *******
unfortunately legally you must show a return ticket . Even you have a long visa . The law is that everyone who fly to countries like Thailnd Costa Rica and many other say you need a return ticket . That what the airlines are obligated to check ! Often the airlines have not undated system about the long term visas . There system just just say “ must have a return flight “ . Yes it depends if they check at counter actually check that or not . Yiu had a stubborn one unfortunately. Reason for airlines to check is that they are liable for the guest and must pay for the flight return in case you are refused at the border patrol . So emigration can not be blamed for that in any country. Sometimes they not accept train / bus / ship travel back either . So if you travel often you know to have a “ return ticket “ you can actually buy them for 10 $ . Online. Now don’t blame me for this rule ….