Just to clarify my previous post.
KL might check that you are eligible for a VOA which requires on onward ticket. Or you apply for an e-Visa.
If KL check your return ticket to board at SIN, That is fine for RT 1. But they might object when you board at SIN for RT 2, as they refuse to sell the same-day return ticket.
All this seems a bit dependant on being sure to be able to OLCI and get the KL e-BP from DPS.
If you don't get it, you will have to go through immigration at DPS and, even without checked bags, the 1h10 turnaround is too short for that.

PS: I have no experience in such transit at DPS, just normal arrival and departure, and it can be quite slow.