If you are over 50 get a Non-O Visa to remove the requirement for proof of onward travel, get you 90 days on entry relatively risk free and no need to visit Immigration. Well worth the cost.
That's a first, seasoning for a marriage Non-O (Jomtien requires it for a retirement Non-O). Did you get this in writing as a printout as people are often "told" incorrect things even at Immigration?