Hayden Singh was a member of Starfleet, a Human descended from the peoples of India on Earth. Singh served as supervisor of technicians aboard the USS Enterprise in the 2260s. Early in the five-year mission, Singh had a reputation of riding all the technicians hard, and was particularly unflattering of his views of command division officers who were just passing through his departments.
Lieutenant junior grade Singh was working in one of the ship's auxiliary bridges when James T. Kirk brought the Nomad probe to him for data transfer star charts from the computer.
Later in the Enterprise's mission, one of Yeoman Singh's assigned duties as a technician were shifts working in laundry and recycling in the lower decks of the secondary hull, where he had gone so far as to work with Yeoman Brunowski to rig a warning system to let them know when a senior lieutenant was approaching the laundry area.