SQ and CI lounges are both at Terminal 2 and pass security and immigration control. Once you pass immigration, you'll need see the stair cases, you'll have to go up one floor, then you'll see SQ lounge there.
CI lounges, you'll have to walk toward gate D area, right after you pass immigration, you'll have to turn left, and once you get to the end of the hall way, turn right, you'll see CI lounge.