Bangkok is one of the world’s great cities, all of which have red-light districts that find their way into the pages of novels from time to time. The sex industry in Thailand is smaller per capita than in many other countries. That it is more famous is probably because the Thais are less coy about it than many other people. Most visitors to the kingdom enjoy wonderful vacations without coming across any evidence of sleaze at all. Indeed, the vast majority of Thais follow a somewhat strict Buddhist code of conduct.
On a related topic, I am bound to say that I have not myself come across police corruption in Thailand in any form, although the local media reports malfeasance on almost a daily basis.