Keep the original and provide explanation. Your visa has been issued, it's a done deal. Doubtful that you'll be questioned that deeply unless you are applying in country for an extension, which isn't recommended.
After the interview you should get the decision fairly soon. Surprised they didn't tell you the answer at the end of the interview. If approved you print out your visa, grab your passport and head to Thailand.
Total scam, immigration is only concerned about the most recent TM30. I advise you to stop doing past history storytime with landlords and just request the TM30 they are required to file