Sak Yant, Yantra Tattooing

Yantra tattooing, also called sak yant (Thai: สักยันต์, Khmer: សាក់យ័ន្ត), is a form of tattooing practiced in Southeast Asian countries including Cambodia, Laos, and Thailand. The practice has also begun to grow in popularity among Chinese Buddhists in Singapore. Sak means "to tap (tattoo)", and yant is Thai for the Sanskrit word yantra.
Sak yant designs are normally tattooed by wicha (magic) practitioners and Buddhist monks, traditionally with a long bamboo stick sharpened to a point (called a mai sak) or alternatively with a long metal spike (called a khem sak).