what are the rules of domestic helper staying here in china

i am a domestic helper in hongkong i have a multiple visa here in china each stay is only for 15 days but i stay here for almost 15 days and go back in hongkong for 7 hours go back in china again when in fact we domestic helpers are not allowed to work here then why are you giving us a multiple entries ?it is very impossible not to work here for staying long period of time .