Singh drove the green on the par four 16th, but was 80 feet from the flag and three-putted it for a par that kept him two behind.
Warren moved three clear when he two-putted the 12th for birdie and Molinari bogeyed it, but the Italian - runner-up in last week's Alstom Open de France - came back with a birdie on the next.
The new target in the clubhouse was Singh's 67, but leaving a 14 foot birdie chance on the last short probably ended his hopes.
Warren threw away his advantage with a double bogey on the 15th. He was in the right rough off the tee, got lucky when his second shot found a walkway, but then three-putted from 20 feet, missing his bogey attempt from three feet.
He was level with Molinari and one ahead of Singh and Swede Alex Noren.
|1||SINGH, Jeev Milkha||IND||18||-17|