I found a place near me that teaches MT. Is this a McDojo?
Cardio. Aerobics. These things are overlooked in every Kung-Fu/Karate/Tae Kwon Do school I've ever been to, yet it is the single most important thing if your fight last more than 1 minute. Not only will it improve your martial arts, but it will make you better at everything in life. So go run 2 miles.
The Kun Khmer place you're talking about produces good fighters and regularly puts on shows, so I'd say it's worth a look. Kun Khmer is essentially the same as Muay Thai (don't say this in front of them, though).
The other gym you linked to don't have much of a fight team these days (or as far as I know), and they're big into contracts, but it doesn't hurt to go try them (except the $20 trial class fee, which is a bit steep IMO).
Also in Dandenong (I presume you live near there?) is Young Bulls Gym, who produce some good fighters. In Noble Park and Narre Warren there's XFC, which I think is more kickboxing, but I'm pretty sure they have a fight team. A bit closer in on that side of town is Martial Mix in Glen Huntley.
If you're willing to travel to the inner-city, there are some good gyms in Richmond and Brunswick.
Anyway, here is a site with most Melbourne Muay Thai gyms on it. Details of all the above places should be there.
I've contacted several members of that Kun Khmer gym via forums and Facebook. By the sounds of things it's a great place to train, and the rates are extremely cheap - $5 per week, and you only have to pay it IF you train that week. I'll be checking it out pretty soon.