I noticed that when I entered on Monday. I saw some Indians being questioned by officers at the flight gate and saw a lot of people sent away by officers. I guessed it was to complete the TDAC but that's just a guess.
Depends on the IO. I entered Thailand probably 10 or 11 times visa exempt last year but majority of my trips were for 2 nights with longest being for 2 weeks.
If you're here for 30-90 days per trip then you have a higher chance of being flagged as they may suspect you of living and/or working in Thailand.