I have been through the Thai border twice in the past couple of weeks.

First time there was no mention of the TDAC and everyone was sailing through. I assumed that the immigration officer had found the TDAC linked to my passport and nothing else was required.

Second time it was much more chaos. Many people were being rejected from the immigration desks for having no TDAC. I had managed to mess up the arrival date on my TDAC (my fault, too many flights) and therefore the TDAC wasn't paired with my passport for entry that day, and the immigration officer couldn't find it automatically. They needed the 🕖 character approval code to find the TDAC in their system and they kindly modified my arrival date and sent my on my way.
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So based on my experience, I wonder if the first time they were choosing to not enforcing TDAC, or everyone had their TDACs present and correct? Second time there was obvious enforcement, people being sent away to apply there and then.

You can update the TDAC once it's been applied for to change data, so if you notice you make a mistake you don't need to do a new one, just update the one you already have. I was initially asked to do this (there's a QR code on the window of the booth that takes you to the TDAC create/update page) but the immigration officer took pity on me and said "hold on, I'll do it for you this time". Big 🙏 smile and thankyou.

Oh, and as you begin your descent into Bangkok, Qatar will play a specific BKK arrival video which, wait for it, includes filling in the old paper form 🤦‍♂️ and no mention of TDAC. Lovely.