I've read your update. 🤬 What. A. Shit.
Have a heart to heart with the sensible brother - what does he know about all this?
Are all the men on this trip with wives/partners? Do they have mums, sisters, aunts, adult daughters?
I'd be having heart to hearts with every one of them.
Share what people who know what they're talking about have told you here in no uncertain terms exactly why men go to Thailand. And it's not for the scenery. Send some reputable online links.
And keep sharing it. Make sure they know exactly what is being planned. You could spare some woman or child at least one ghastly customer.
And then share what your husband's just done to you - because are they pulling the same trick themselves? Keeping the wives on their toes?
You've got an army of disgusted strangers right here.
Build a smaller army of disgusted female relations who are part of their lives and may support you and give this family of shits hell.
There's a saying - revenge is a dish best served cold. You could either let him know this so he's kept in agony waiting for when/if yours is served years later, or let him think he's got away with it and relax, then ...
But I have a feeling this whole thing may be your 'punishment' for going away yourself - his dish served very cold indeed.
Most importantly, look at the rest of your relationship - is this a one off or does he have form for treating you like this?
Do not take this lying down.