No you need more time. While theoretically possible to make the connection it is a high risk one.

You may or may not be able to through check bags - there is no obligation to under separate tickets and BLR check in may view the connection as risky thus not through check bags. You will not be able to check in for UA at BLR. You need your SQ flight to arrive at SIN on time, get off the aircraft quickly and reach the transfer desk in sufficient time to check in before United closes check in for their flight. That is possible, but unlikely.