Yellow Fever

I just arrived in Bangkok and I was traveling from Brazil so I already had my yellow fever vaccine and of course all the other necessary documents. Then when I go the lady immigration officer, she wasn’t too friendly and she told me I had to go to the doctor inside the immigration center and get a quarantine form! I was absolutely shaken. I thought they were going to tell me I had to quarantine for X amount of days. Nevertheless, I went to the doctor and she asked me where I was so I said Brazil she asked if I was staying in Bangkok and where I was staying so I gave her the AirBnB in Bangkok. There was no wait and it took all, but a few minutes. Then I was able to skip the queue and the man asked me nothing and stamped me in. No idea what the point of the extra form was. Has anyone had this happen to them?