According to the clues, plotting the points on a number line, we get

As S is the least of the given integers, it is placed at the left most end.
Since R is the smallest positive integer, it is placed next to the right of 0.
As Q is 2 units to the left of R it is placed as the left next number of 0.
P and S are at the some distance from 0. P is placed opposite to S.
∴ Ascending order : S < Q < 0 < R < P.