In Thailand it is customary to acknowledge, honour, show respect and thankfulness to your teacher. A Wai is the prayer like coming together of ones hands, and Kruh is teacher. Here, the children were showing their respect to their teacher, who in turn is giving them his blessing before a martial arts display. I might add, they are real swords, real metal, real sharp.
Also I'm finding out that medium format film cameras are great fun, but at their best with non-moving subjects :-))
