Hello,
So there are a few gyms in Montreal, it really depends what you're looking for. Most gym are (if not all by now) multi sports gym.
I know they were two brothers, I believe they were from Cambodia or Laos, but practicing their version of 8 limbs fighting, but I can't find them on google.
But for gyms here is a quick review.
Académie Frontenac. Mostly for beginniners and people who want to be fit. Classes are both boxing and muay thai and often the coaches are not muay thai guys, they will just add a kick at the end of a boxing combo. But the main coach, is really good and if you're into advance classe, fighting and sparring, then he's running these classes. Also, pretty cheap and lots and lots of classes for anyones schedules.
Underdog Boxing. Primary a boxing gym, a very good one (you'll see pros like Jean Pascal train there once in a while), run by two brothers. They have a muay thai "program" run by two other brother, I believe there is only 3 classes a week, tuesday, thursday and saturday. Also very cheap. The advanced team is good, fun sparring, fun training. The two brothers are pasionnated and fun to train with.
Thai Long: never trained there but it has a good reputation, they do pretty well in local competitions.
Titans: Pretty good main trainer Kru Ash, active and involved in the Montreal and eastern canada muay thai community. Never trained there.
Skarbowsky Gym: So Jean-Charles Skarbowsky is apparently taking over the world, he has gyms in France, China, Thailand and now Montreal. I don't think it is open yet, but should open soon. You can contact him on facebook I am sure he will respond. But he obsviously won't be there on a regular basis and the main trainer he choose to run the place seems a bit of a knuckle head, but I don't actually know, I only base this judgement on his facebook profile.
Tristar: don't go, their muay thai guy suck and they always lose in local fights.
Finally, I got a friend of mine, Ben Rancher, he coaches at two gyms but also in his garage with a small group of people. He's awesome, nice, respecful and very good. You might want to try this. I don't know how much it is. Here is his instagram. https://www.instagram.com/ben.rancher/
Good luck