To be precise this would be spelled כן, wouldn't it?
I wonder what other ways there are to say 'Please...' when asking for something? In another thread I have recently read that בבקשה is more commonly used in the sense of Don't mention it! You're welcome!
I think na is attached to a verb to say 'please do something' shmor-na please keep I'm not sure if this is right!
Although it would usually come before the verb when it comes as a standalone word. It's not very common to say it though