Why Did Immigration Police Visit My Condo in Thailand?

FYI. Today, for the first time in six years of residence in Thailand, the immigration police came to look for me at home, took a picture of me with my partner and made her fill out a form, in Thai, that I had to sign jointly with her. I am surprised, frankly. I felt under investigation. At least fifteen Asian immigrants, unknown to the immigration police, have been living in my condo. I mean, I have nothing to hide or any reason to be afraid, I just wonder if paying two men to verify foreigners who are used to do the things according to the rules is not a waste of public money and a merely demagogic action. But that's it. I hope not to be out of topic, sorry.