From the period when Sabah joined the Federation of Malaysia in 1963, stamps from each of the states were eligible for use throughout the federation. For these reasons, stamps from Sabah were sometimes found commercially used with Singapore cancellations. They were also used in the other states but were usually as part of a philatelic cover.
The following high values should not have been that commonly used in Singapore. I have yet to find Singapore stamps used in Sabah during this period. There could be some but they would be quite uncommon. Was Singapore running out of high value adhesives (their highest value was $5) or was it that Sabah had a surplus of these stamps that they rather see used elsewhere including Singapore?
A montage of these two $10 stamps gives a clear impression of the parcel cancellation for Killiney Road Singapore 9. The Killiney Rd post office replaced Orchard Road in 1963. Proud only gives a solitary date of 16.9.63 but it was probably more common than that.
This is another parcel cancel quite likely to be from Singapore as well. There are not enough visual clues to be certain of its origin.