I presume FL is in a budget hotel? Cos other hotels you should not even be going to the counter... it should be straight up to the room ah...
If budget hotel and you are the one booking, then yes, they will need your IC. I used to go with my FB who is PRC. She also has to show hers. Safest that way. Take it as quickie for a couple. Drive along Balestier Road and you will see quite a lot of such couples
And like the other bro said, make sure not underage.