The Singapore Ranger's course is something reserved for
the "elite" troops of the SAF. CDOs will find that
the Ranger course is compulsory (whether you like it or not) and there will
be the very "enthusiastic" regulars who will sign on to do it for
the heck of it.
This course was based on the American Rangers School course.
However, do not let this deceive you.
In the US (based on what I know from living there), the
Rangers are not considered to be particularly
"elite". In fact, their job for the entirety of WW2 was to
simply capture airfields and provide forward
reconnaisance.
You might also find it interesting that the US Army doesn't
carry as much weight as say, the US Marines.
So in general, you could say that Singapore's version might
actually be harder, considering the military population that it is
catered to. Even though it was developed initially in the US,
of course.