This kind of scam goes on all over town. For example, if you look at the ads for short-time hotels, they often have Thai fine print at the bottom saying that girls who bring farangs there get a kickback.
Best one is the pushcart vendors who sell those big fook-off stuffed animals. Ever wonder why they look so ratty if the vendor is selling them every night? It's because when a farang buys his date a stuffed animal, she can bring it back and get a portion of the money back from the vendor. So, they're the same stuffed animals sold and returned month after month.