Hi Roosh,
Not been to Banchamek, but trained at Fairtex a long time ago. Way over priced in my opinion, and wasn't the best. For my money I'd well recommend Petchyindee. Petchyindee is not cheap either, but top name fighters and flexible training packages. Very nice accommodation/food you'll be well looked after. The gym is in a non-touristy part of Bangkok though, so just a heads up - there isn't much around. If you make it there, be sure to train with Kru Wat - its an experience