You're considering it? My advice is to take it for 6 months and then decide if you want to stay. You will cover basics that are pretty boring as far as I'm concerned but around 6 months you should be sparring and doing advanced drills. Be patient to see if it's for you, I hate it when people join something and don't give it a chance not realising that it takes time to get good and do advanced work, people always want the quick fix. Be wary of cardio kick classes masquerading as Muay Thai!
i have to aggree and disagree with damain mavis. he's right that the first 6 months is boring, but thats the condition period. its all basically the same stuff for 6 months and some ppl start to think MT is ********. but that 6 months is to build endurance. After the conditioning , work hard on your techniques. after your first fight, dont quit muay thai (most beginners tend to do that), come back and you'll notice the diffeence in your training. i cant explain but you'll see. trust me