It's very straightforward, go to Nana Entertainment Plaza in Bangkok, visit Cascade Bar - get there around 6 pm. When you see Cindy, buy her a "ladydrink", chat with her and if the chemistry is good, agree to a price for her services, and bar fine her for the encounter.
Everything is OK, except the timing. 6pm would be terribly early. I assume, you ment 9pm.