First of all, the most common kind of prostitution in Thailand is an economic, not a moral, issue. Most prostitutes come from the poor farming northeast ("Isaan") and speak a Thai-Lao or Thai-Khmer dialect. They have a 6 year government education from a country school (after that, it's not free). Their employment options are $100 per month jobs in factories doing 6 day weeks at long hours, or similar employment ... or far more money hanging around foreigners, getting exposure and learning real life things, and hanging around with their friends.
Most of them send a big chunk of their money back home to their family. Most don't take drugs or even smoke, and many don't drink alcohol.
It is cultural arrogant of people from wealthy countries to come here and preach about morality. Try having their background and their options.
In comparison, in rich countries there are many "matrimonial prostitutes", i.e., women who prefer to marry a rich man who will support them rather than work for their own money, pursue a career of their own, and find someone with a similar purpose in life, similar interests and similar values. Many people in rich countries never have enough money, and are very materialistic. That is more morally questionable.
However, in Thailand there is an increasing trend of young students entering prostitution in order to buy fashion items. There are also prostitutes who are addicted to gambling, alcohol and drugs. Plus there are scammers. Like the matrimonial prostitute, this is a moral matter of values and interests, not an economic necessity.
Forget Reform or Purpose