Research has shown that there were female monks in Thailand. It might sound like an arcane point, but in fact it is vitally important, because the claim that there never were is used to deny women the right to full ordination.
The nuns you will see around traditional Thai temples – dressed in white not saffron – are treated as little more than servants, and are not fully ordained. And even more importantly, in popular belief they can’t help their parents to heaven, as male monks do with even a few months in the temple (as most teenage boys do).
And since there’s a traditional that children must “pay back the breast milk”, girls have to do this instead by making money. And the only way that lots of girls have to have at least the possibility of making lots of money is through sex work – sex work that often starts very young, and could never be reasonably said to be a free choice.