Thanks a lot!
I am familiar with the layout and setup of SIN, have been there many times and most recently a few weeks ago, but never arriving on SQ and never had the need to take my morning shower there. That's why I didn'^t know whether the SQ lounges could also be used as arrival lounges, Good to hear that they can.
BTW, on one of your above questions: La Premiere used the QF First Class lounge. Well...