I'm actually a Muay Thai trainer at the Aliso Viejo and Fullerton locations. For the most part the classes pretty much goes like this:
15 min warmup: Coordination drills, calystenics, basic punching/kicking drills
5-10 minute stretching
30 minute boxing/kickboxing/MT drills/combinations on bags(depending on the class): usually consists of basic drills(technique/footwork/timing) then followed up by combinations using the techniques learned in the drills.
5-10 minutes abs
Instructors classes vary. Some focus more on technique, some cardio and some both. The classes are a good foundation but to be able to compete on a higher level I would suggest getting private lessons with an instructor. All of our instructors have had at the very least, extensive amateur backrounds, most have competed at a Professional level and have plenty of knowledge to pass on.
PM me if oyu need any more info