if you are not into the usual bkk fare ie soi cowboy,patpong or nana,
i suggest you could try G-clubs like carribean, but bear in mind you may go back empty handed. You could possibly hit tunnel or lucky after that though.
Another place i heard is good is calefare which is near carribean where many gals go to after their work. Alternatively, you could try scratch dog at windsor hotel, sukhumvit soi 20. A good place with many puyings and its very squeezy.
There are other good discos like JET, CURVE or those along RCA. mostly thai crowd with good live thai band.
or if you are really adventurous, you could stake out the shopping malls like emnporium, paragon, siam square during the afternoon. You may just get lucky by pretending to be a "newbie" in bkk...
I personally have tried the starbucks at lang suan ( same soi as tunnel), you find many uni gals there in sch U studying there.
For soapies, there are plenty in ratchada famous stretch. I shall not elaborate on this.