can my ISP monitor what websites i visit?
Yes.
But there are ways to prevent it. Why do you ask?
because if i was 1 in a million user on their network,i wouldn’t care,however,this place being a microcosm,my ISP is a local company,i even work with some persons doing part time work there,so, errrrrrr, better stay off the dodgy stuff like forumosa then
Especially the childporn here … 
checking out dragonbone’s bread recipes can have you put in jail 'round these shores