eBooks 
You will notice that many Thai Massage beginner courses are organized as thirty-hour five-day trainings (30 hours spread over 5 days).
Nonetheless, this is certainly not a rule and all depends on what the contents of the training course or workshop is, but spreading thirty hours over five days is a good common practice that has proven itself.
eBook | More info here
In fact, the whole thing is not so much about thirty hours, but about having six hours effective training per class day. Those six hours has shown to be the perfect fit; rather intense, but not too intense.
Now, how to arrange those six hours on the day? Well, I basically always did it like this: I would start at 8 am in the morning, two hours teachings, followed by a break at 10 am until 10:30 am, and then again two hours training until 12:30 pm.
At 12:30 pm, I would take a break of one and a half hour so that the students and I could have lunch (for about half an hour) and then rest and digest for at least another hour.
At 2 pm, I would continue the classes until 4 pm. That would make a full class day of six effective study hours. Then I’d give the students the option to practice by themselves under my supervision from 4 pm until 5 pm.
I think that the sequence of dividing up the six-hour day into chunks of two hours is perfect. Two hours in one go is a good time span to really convey info, knowledge and practical skills, but longer would be too much for the average concentration span.
