According to this article MS could start flying to SIN again. They used to fly 2x weekly CAI-SIN-SYD A340 flights but axed the route in 2002 after the drop in passengers numbers following 9/11. Airline officials stated that the 65% loads experienced were not enough and the route was loosing money.
The article also seems to mention SQ increasing their CAI flights. They currently have 3x weekly SIN-DXB-CAI flights with B773s (they have passenger rights on the DXB-CAI route).
Currently MS code share with SQ's flights to SIN and Australia (MEL and SYD).
http://sg.news.yahoo.com/050507/5/singapore146320.html