“Modern slavery” isn’t a figure of speech. It has a specific meaning describing worker exploitation.

For example the UK has the Modern Slavery Act - https://en.m.wikipedia.org/wiki/Modern_Slavery_Act_2015

I mean, it’s at least arguably an allegation of a crime. I wouldn’t be a fan of criminal libel still existing, but that’s a case where it might be appropriate for the hotel to take a civil libel case, assuming it’s unfounded.

Which, considering this is Thailand, probably is founded indeed.

Nice downvotes. I don't get how people can be so oblivious to the fact that Thailand is one of the major hubs for modern slavery, especially when it's so well publicized but, well.

Context matters, in this case location.

It’s like joking about child prostitution in Cambodia. As an American it’s something that happens in far away lands (not entirely true, it happens in the US too).

In Cambodia, it’s a very serious issue that really pisses of locals since it’s mostly Western tourists supporting it there.

Joke about it in the US and it’s just frowned upon. Do it in Cambodian and you’ll piss people off enough to get yourself in trouble.