Having a fling with your boss is a complex thing because you don't want this story to impact negatively on your career of job.
It is complex because he is in a position of power and sometimes using his influence as well to get to you.
If you want to play it safe, the best is to keep it on a light flirting ground.
If he goes too far, set up a boundary and educate him on that.
Now, if you are expecting a committed relationship with him, wake up now!!!
Before you take any step, find out if he is married or in a relationship.
If he wants to be intimate with you, find out first what the rule of the game is.
If you don't want to get hurt, you have to be very smart and not let your expectations rise high.
These are tricky waters!
Stay awake and aware!