According to Thai medical theory, the pathways through which Prana (vital energy, similar to the Chinese concept of Qi or Chi) flows connecting Vata (or energy center) to the sensory and excretory orifices. The Sen are somewhat comprable to the meridians of Chinese medicine but the names are Sanskrit in origin and are derived from the yogic theory of India. This is one of many examples of Thai medicine as an amalgam of the Chinese and Indian schools.

The ten primary Sen are: