Hello, I'm from Finland.
A few years back (2016-2018) I went to Thailand, and did several visa runs to Malaysia and Laos. So I stayed in Asia for about 2,5 years. Then, one time at Don Mueang, they almost denied entry, took me to a separate area where I had to show them how much cash I had. They went thru my passport stamps and calculated how many days I had spent in Thailand, altogether. After about 2 hours, someone told me they can let me enter Thailand just this one more time, but that I'm somehow "marked" in their computer system and would be denied entry next time if I come back to Thailand without a visa or with just a tourist visa. They also mentioned both Don Mueang and Suvarnabhumi airports.
I was wondering if anyone else has experienced this? Also, if I were to go to Thailand again, and they deny entry at Suvarnabhumi, is it possible for me to choose the destination and go to Malaysia (or some other country) instead of going all the way back to Finland?