Technically speaking, at time of check-in, your passport is checked for validity/expiration. Some airlines do it better than others.
My wife had same issue two years ago, checked in at JFK, boarded flight to Seoul. Several days later, at Incheon airport, when checking in to fly to Taiwan, was denied because this time they did check. Fortunately we know folks in Taiwan and had it resolved. But she could not continue onto to Singapore until she got a replacement passport in Taiwan at AIT.
Back to OP's question - it's both whether Singapore Airlines will let you check in/board, and if they do, when your land, will immigration let you enter. Lot's of 'ifs'....