Everyone know Thailand has so many Brothel , just in Bangkok there is over hundreds of them but the it is still illegal. Those brothels run their business in the grey areas, a lot of corruption and they do not pay tax.  In 2015 Havocscope said that about $6.4 billion dollars in annual revenue was being generated by the trade, a figure which accounted for 10 percent of Thailand's GDP.

For most of people when they hear that Prostitution in Thailand is illegal it's like a big Joke, because everyone can see so brothel everywhere in Bangkok and Pattaya.

Prostitution in Thailand must be legal !, just make it like a real business to show their accounting, income and revenue and be able to collect their tax. Thailand can use this tax to improve some Thai people life which is still have a lot of poor in many many suburbs. Also the government will be able to check the disease of those prostitutes , register them and make them an ID card to prevent the trouble between prostitute and tourist ( ie. payment , robbery , harassment , etc.)  so Tourist can pay them via application that tourist can register online to show their identity.