According to
http://www.changi.airport.com.sg/cha...ervices.html#1
there are lockers in the transit lounge (before immigration and customs), but are only available between 7am and 10:30pm. So that won't be useful for the UA SIN mileage runners.
Has anyone used the 24 hour luggage facilities in the basement level in Terminal 1 West (after immigration and customs)?