Kammatthana means the place of work, and by extension the objects of meditation given to a practitioner. The tradition that carries the name is a Thai and Lao movement of wandering forest monks, and it took its modern form under Ajahn Sao Kantasilo and his student Ajahn Mun in the northeast of Thailand at the turn of the twentieth century.
Its context is a reform. Through the nineteenth and early twentieth centuries the Siamese state was centralising the monastic order, standardising ordination, imposing Pali examinations and bringing village monasteries under a national hierarchy administered from Bangkok. Learning meant textual learning, and it meant the capital. Ajahn Mun's response was to go the other way: the ascetic observances of living at the foot of a tree, eating one meal from the alms bowl, wearing robes made from discarded cloth, and walking from place to place through forest that was still, in his lifetime, genuinely wild.
The practices he taught centre on mindfulness of breathing, on the recitation of the word buddho as a way of gathering attention, and on the contemplation of the parts of the body as a corrective to attachment. The emphasis throughout is that these are to be done rather than studied, and that a forest is a better teacher of impermanence than an examination hall. The movement's standing rose steadily through the twentieth century as its monks became known for exactly the qualities the centralised order was thought to have lost.