The Dutch midfielder joined on a temporary basis from Villarreal at the start of last season and the Swans brought him back to the Liberty Stadium for this term.
De Guzman scored twice in the Welsh outfit's 3-0 victory over Norwich City on Saturday, which took them seven points clear of the Premier League relegation zone, and Monk has admitted that the 26-year-old has become a huge part of how Swansea play and would be an "important" permanent acquisition.
"I would imagine he is a player who is at the top of our list - he is a very good player and he suits how we play," he told reporters. "Technically he is very good, he can play in several positions, and you always want players like that.
"He was my man-of-the-match today, his movements and desire to get the ball back in an unfamiliar role were excellent and he was rewarded with two goals.
"He enjoys it here. He has thrived here so he would be an important signing, but we have to speak to the player and see what he thinks."
De Guzman has made 87 appearance for the Swans over his two loan spells, scoring 15 goals including a brace in their Capital One Cup final success over Bradford City at Wembley last February.