The contemporary practice of spiritual healing as a metta meditation of loving kindness has its roots in the Buddhist temples of South East Asia. If one traces the evolution of the ancient healing techniques practiced in Thailand, Laos and China over the past millenia, one discovers the earliest roots lie not in Thailand but in India.
The legendary founder of the art is believed to have been a doctor from northern India known as Jivaka Kumar Bhaccha, a contemporary of the Buddha and personal physician to the Magadha King Bimbisara over 2,500 years ago. The teachings of Kumar Bhaccha probably reached what is now Thailand at the same time as Buddhism – as early as the 3rd or 2nd century B.C.
The theoretical foundation for all of these practices are based on the concept of invisible energy lines running through the body. The Indian origin and influence is obvious here since the background of this theory lies clearly in Yoga philosophy, which states that life energy (called Prana) is absorbed with the air we breathe and with the food we eat. The network of energy lines, the Prana Nadis, supplies the human being with vital life-force energy. Work with these invisible energy lines has traditionally been considered a spiritual practice closely connected with the teachings of the Buddha, and it is only recently that such healing arts have ever been taught and practiced outside of these Buddhist temples.
Traditionally, the work of healers has been understood as a physical application of Metta, the Pali (and Thai) word used in Theravada Buddhism to denote 'loving kindness', performed in a meditative mood, starting with a Puja (a meditative prayer) to fully center to focus on the work, maintaining full awareness, mindfulness and concentration.