The 28-year-old has proved a valuable Raiders player, playing all 20 matches for the club this season following a knee injury that sidelined the forward for the second half of 2017.
The forward will now stay as one of the Raiders until the end of 2021, his experience vital in pushing the club forward and creating structure in the forward pack.
Peter Mulholland, Raiders recruitment and high-performance director, said of Lui that his re-signing will prove an important strategic move for the club.
"Dunamis has shown wonderful commitment and professionalism to return from a serious knee injury and play every match for the club this season," Mulholland told the club's website.
"He's an experienced first grade player who will be a valuable part of our squad in the next three seasons.
"Dunamis has been a consistent performer for us this year and we are looking forward to him continuing on his good form with the club."