I do Thai boxing. Why do you ask?
I started but it was too much for me with work, but starting again monday I hope! Are you planning to become competitive? Where are you from?
For me it took bout 10 trainings to adjust. Wasnt just the cardio but my shoulders and upper back werent used to the tensions and hits. Took alot longer for my chins to adjust to the lowkick sensation.
I used to kickbox last year. I absolutely loved it. It was more MMA mixed with Thai. I only stopped because I couldn't afford it anymore.