For locals the rate is 70k for 20 mint and 100k for half hour. As you are Chinese, you can only use your mouth when needed up to the point at which you have already got the payment done with. A simple nod of acceptance with the girl and walk in present the cash would be the way using fingers as time/money communication. You can even act like your tongue cannot talk (disabled) ... that way as long as you dress like a "Korean" then it can be hard for girl to think your "foreigner" haha but I think that's very cheap. But funny.