Thatha is a custom generally existing among the people in Kinnaur District
of Himachal Pradesh
. It is designed to protect themselves against assail of evil spirits and ghosts. This custom is observed once in every three or four year.
During this occasion, the whole village becomes beautiful with the brightly lit one hundred and eight clay lamps. It is believed that the illumination of lamps bring brightness into their life. Afterward, a special puja is offered to Lord Vikyu (a village deity) in every house.