Can a slave ask a favor?

Absolutely.   

But asking is not the same as receiving.   

In fact, sometimes it is the opposite, or there may be payment required first.

Last night I was on my knees next to him and reluctantly asked him if I could ask for something.  (This is my indirect chicken shit way of sneaking up on topics that I don't like to talk about.  Asking for special favors of things he may not like to give is one of those things.)

I asked if the next time we played in public if he could please not ask me repeatedly if I wanted him to stop, because it seriously messed with my head and was worse than anything he would do to me physically.   It messed with my head in a bad way, not the good way from This post.  It makes feel TOO MUCH IN CHARGE.  Which, though deep down I know I really am not, I don't like to feel even a little bit, especially when I'm trying to get into the headspace of playing.

 He doesn't do it when we play alone.  Well, occasionally he asks in an obviously taunting way, (it is easy to tell a serious tone from a taunting one)  but in public he seems to worry about me not actually enjoying it, or possibly when I am more stiff in my reactions, because of people watching and nerves, it makes him feel like something is wrong with me.    I think he took my concern seriously, and he said he could do that for me.  I promised that if something were seriously wrong, and not just my nerves or not being warmed up, I would let him know. 
 
Then came the payment for future favors.  He proceeded to painfully twist my nipples while asking me if I wanted him to stop, barely giving me a chance to squeak out "No, Master",  as he was saying he really didn't fucking care what I wanted.