This is a rare statue depicting Shakyamuni in the early part of his journey towards enlightenment when he was practicing asceticism.
From Wikipedia:
The historical Siddhartha Gautama adopted an extreme ascetic life after leaving his father’s palace, where he once lived in extreme luxury. But later the Shakyamuni rejected extreme asceticism because it is an impediment to ultimate freedom (nirvana) from suffering (samsara), choosing instead a path that met the needs of the body without crossing over into luxury and indulgence. After abandoning extreme asceticism he was able to achieve enlightenment. This position became known as the Madhyamaka or Middle Way, and became one of the central organizing principles of Theravadin philosophy.