There is also the chance that someone else with very similar information kinda matched your p/p and he was just verifying that you were not the “bad person”in question!
Just as a note: The checking flow goes - check birthday, check name and see if there are similarities needing closer scrutiny. If needed they will see every time you have passed through immigration for the past 10 year even if using a different passport.
In literally hundreds of entries into Thailand, I have never been asked to show on onward ticket.
BUT, I have flown many airlines and everyone of them has demanded an onward ticket or NO boarding pass to go to Thailand. Reason: IF immigration denied you entry for this reason, the airline is responsible to fly you back to your starting point.
I did a change of address and 90 day report at Korat Immigration a few weeks ago. I didn’t need any forms as both officers (ladies) did it all for me in their computer system. The whole process took less than 30 minutes.
When I updated my new passport info a couple years ago (Bangkok Bank Siam Paragon), they didn't even tell me what they were doing until they were finished. They actually CLOSED my account and opened a new account with the new info.
I actually did use an agent when I was in Bangkok. I found it well worth the fee. I have seen some agents that claim they will “take care of” the bank issue, but I’ve stayed clear of someone offering what is obviously questionable.
I used Fast Track last week when returning from a trip to Hong Kong. Long lines at the regular immigration counters but Fast Track was NO wait. Also, my under 70 wife can use Fast Track because she is with me.