What is the process for entering Thailand on a DTV visa, and what should I expect at immigration?

Recent experience entering on my DTV visa 3rd entry. I was returning from Vientiane Laos by land before flying from Udon Thani Airport. During my land crossing I was asked to go to the back and see the supervisor. No questions about purpose of my trip just looked through passport and sent back. I walked to the back room sat down handed the supervisor my passport. He looked quickly and said do you have a visa? I said yes it's in my passport. Apparently both him and the first immigration missed the physical copy of my DTV inside my passport. I asked him to hand me my passport opened and showed him the DTV. He took my passport back stamped me and told me have a good trip. Zero questions about current activities or purpose of visit. I had my TDAC done as well and they didn't ask for my QR code. So all in all if they had seen my visa most likely would have just waved me in. Next time I'll just make sure my passport is open to the DTV page not my bio data page when I hand it to them.