@Tom ******
Each immigration office has their own TM30 policy. According to the form, it's used whenever you stay (*NOT MOVE*) at a new place.
For example:
January 10: You arrive in Thailand, and stay at a hotel. The hotel will file a TM30
January 20: You decided to get a long-term rental for an apartment. You (or your landlord) would file a TM30.
February 1: You decided to take a vacation in Phuket. The hotel in Phuket will file a TM30.
February 5: You return back to Bangkok. You (or your landlord) will file another TM30.