Ruiz, who moved to the Eindhoven outfit in January from Fulham, netted his first goal for the club when hitting the winner in a 2-1 victory over Heracles last week.
And he produced a decisive strike once more on Saturday, his low effort being followed up by a fine 82nd-minute goal from Memphis Depay to earn PSV all three points.
A power outage did not ignite proceedings at the Abe Lenstra Stadion as Heerenveen and NAC Breda played out a drab goalless draw.
The home side went into the game aiming to enhance their hopes of UEFA Europa League qualification, but that did not materialise.
Bilal Basacikoglu spurned a golden opportunity just before the end of a match that had earlier seen the first half cut short by floodlight failure.
By contrast, Cambuur's Paco van Moorsel made no such mistake when he was handed an opportunity to earn his side all three points late on against nine-man Roda.
Bottom-of-the-table Roda were derailed during two minutes of madness just before the end as Kees Luijckx and Guy Ramos were both sent off for second yellow cards.
That paved the way for Cambuur to snatch a win when Van Moorsel fired home in the closing moments.
In the day's other game, Furdjel Narsingh's 92nd-minute equaliser earned Zwolle a draw against Heracles.
It appeared that the hosts would take the points when Jeroen Veldmate headed home Simon Cziommer's cross in the 40th minute.
But Narsingh had other ideas and his smart finish secured a share of the spoils.
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