I did 40 days and out to Japan for 12 days. After my flight back to BKK they sent me to the interogation room. Maybe because I'm came from not a rich country with weak passport.
The senior officer lady in the room look at my passport and asked on my job and salary, I gave her my work contract and after a few minutes of chat she said i don't know why they sent me there and escorted me to an empty counter to stamp me in. Was an interesting experience.