The event was reduced to 54 holes because tournament officials decided not to play the 18 holes that were rained out Thursday.
In Sunday's second round, Singh shot even-par 71 to finish at 15-under 198, one-shot better than England's Simon Wakefield (68).
It was Singh's third victory on the European Tour.
"I feel very fortunate to win with 18 pars," said the 36-year-old Singh, the first Indian golfer to become a member of the European Tour.
His 8-under 63 Saturday led to a four-shot advantage entering Sunday's round.
Wakefield closed with birdies at three of the final four holes and his second-place finish was two shots better than compatriot Iain Pyman (65), Swedes Martin Erlandsson (65), Michael Jonzon (67) and Pelle Edberg (65), Australia's Peter Fowler (69), who all shared third place at 12-under 201.