The Costa Rican forward linked up with PSV in January after being deemed surplus to requirements at Craven Cottage.
He has enjoyed a welcome return to form in the Eredivisie and is enjoying his football once more - ahead of a World Cup campaign this summer.
His initial loan agreement is due to expire at the end of the season, though, at which point he will be expected to return to England.
Ruiz still has a year left to run on his contract at Fulham, and is yet to work with current Cottagers boss Felix Magath, but the 28-year-old admits staying on in Holland - where he has previously shone for FC Twente - would appeal.
"I am really happy here at PSV," Ruiz told Fox Sports Eredivisie.
"They have a new project for next season to become champions with a strong squad. I would like to be part of that.
"But first we have to see what happens. There are still games left, possibly play-offs, and after that the World Cup.
"What will happen depends on several things. I still have one year on my contract at Fulham."