What should I expect when crossing the Nongkhai border into Thailand on a visa-exempt entry?

tl;dr - crossed Nongkhai, visa exempt, USA passport - no problems

Nongkhai - border bounce. First time I have done a border bounce (coming in on visa exempt). Second time ever that I have entered Thailand without a visa. Five years worth of tourist visas.

I was pulled aside for reasons i am not sure. The other times I have crossed the at Nongkhai, I went with a tour so I was guided everywhere. I didn't have experience with the visa-exempt so I wasn't sure if I needed copies of papers or photos or what I needed, (going into Lao I needed these things).

I asked the lady at the photocopy place and she directed me to room 15 (the principle's office). There was a guy that flipped through my passport and then walked me to the Immigration supervisor. I was not pulled aside, rejected at the counter, or held for further interview. I was simply directed to the supervisor to answer my question about photo copies, or what I needed. Likely a different situation if I knew what I was doing and just got in line like everybody else.

The immigration supervisor flipped through my passport. Gave me the what-for.. She: 'why you stay long time Thailand', me: "no stay long time, I come many times, not same-same". She asked if I had my previous passport - and my dumb ass showed her.. I was trying to be agreable. She flipped through that passport - then said the same thing, "Why you Thailand long time?" and I responded the same, "not long time, many time".. It was friendly conversation, more like scolding me than harassing me.

She stamped me in scribbled something in Thai next the stamp.. Told me it said - next time come with a visa.. She then told come with a visa or get a Thai wife.

I really think those who have problems with Immigration bring it on themselves.