The old men and young Thai women are, unfortunately, totally the norm here. Also old white men with much younger Thai men. It's not just tourists, it's also long term resident foreigners who go with these women.
It's complicated because at one end of the spectrum there are women being exploited. Many of the prostitutes or 'bar girls' are from poor families in the north of Thailand. They tell their parents they work in a factory and they send money home. Many will be trapped by pimps/madams eho they owe money to, so they can only leave if someone (probably a customer) pays them off. Their goal is to get a man to be their boyfriend and give them financial security. Many men 'fall in love' with these women. I doubt many of the women feel the same but I would never blame them for trying to make the best of their situation. Having said that, some are outrageous in terms of approaching men they know are married or have children, but then it is still the man choosing to accept their flirtation...
There are also LOTS of Thai women/foreign man relationships that you wouldn't consider sex tourism at all, but it has a seedy side. The dating scene for non-Thai women here is close to non-existent, because Thai men are less likely to be interested in them and foreign men are often VERY drawn to local women. I have friends who have married nice local women of a similar age, who have a regular job and can speak English, and these relationships seem 'normal' and balanced. But it's a cliche that the woman is often FAR more attractive than the man! And the man is often heavily subsidising not just the girlfriend but also her extended family. This is a generalisation and of course not always the case, but it's really common. Even educated Thai women often want to have a foreign boyfriend or husband.
The worst side of all this that I've seen was in a holiday town just before our first lockdown. I've never been to the sex district in Bangkok so didn't know what to expect. We walked down a street of bars and clubs, empty due to lack of tourists, and there were girls wearing NUMBERS so you could just say which number you wanted. Several times I was approached by men with a menu, and when I looked it wasn't to try and get me into a bar with drinks promotions etc. It was a menu of sex acts to watch.
What's crazy is that Thailand is actually a very conservative society, that just turns a blind eye to this one outrageous (and profitable) industry. The main area in Bangkok for this is located next door to a police station. I'm sure the chief of police there makes more money in bribes than in salary. Prostitution is illegal. Even sex toys are illegal! But the law is a very vague and flexible concept in Thailand...