Why do you think that? Nobody (except posters on this Forum who think they're being funny), including the police and the government, has ever said that. There is substantial legislation which has tried to regulate the provision of sexual services and which allows 'licensed' premises to operate legally. Aspects of prostitution like operating brothels (hence the "bar fine"), underage prostitution and soliciting (the subject of this thread) are illegal. A cursory reading of Thailand's history will show that prostitution, in different forms, has always been part of the culture. Many Thai men have their first sexual experience with a prostitute.