At the start of each year Thailand celebrates Children's Day, a chance to give thanks for the precious lives of Thailand's children - and to let them play with guns and tanks. While zoos and museums are open for free and kids can visit the Prime Minister's office, the main attraction for many Thai children is to climb on a tank or to hold an M16 assault rifle. This year the military free-for-all took a dark and tragic turn at an air show put on especially for Children's Day.