Magic Tattoo festival (or Wai Khru - "Honor the teachers day") held every year in March at Wat Bang Phra.
This place is very famous for it's masters. Temple located about 50 km away to the west from Bangkok (http://en.wikipedia.org/wiki/Wat_Bang_Phra).
A thousands of people come here to make a new tattoo with magic power and monk's blessing (or renew a power of an old one's). It's believed that recipient gets the defensive features or forces of sak-yant tattoo images.
Thai believes that these tattoos will protect them even from real weapons. That's why the majority of the devotees are soldiers, policemen and criminals.
Festival start at night when people come to get a tattoos from masters. These tattoos are created by hand with a long sharp steel needles and special ink made by masters.
Then at morning the main ceremony starts. Crowd listening to monk's chanting and some of the people entering trance-like states, start shaking, yelling and growling as their magic animal spirit. And then start rushing to the main stage where the abbot and monks chant mantras.
Near the stage volunteers wait to restrain and subdue the devotees. They catch rushing devotees and help them to come to their senses by pinching their ears.
At the end of the ceremony monks pour crowd with holy water and throw them a blessed fruits and flowers.