The movie, starring top actors and actresses Jun Ji-hyun, Kim Hye-soo, Kim Yun-seok and Lee Jung-jae, broke the 3 million mark in audience number on Monday, the sixth day since its release, drawing 3.35 million viewers.
It drew nearly 500,000 moviegoers across the country on that day alone, according to official box-office tallies, meaning many of the viewers are those on summer vacation.
The films is drawing moviegoers at a faster pace than director Bong Jun-ho's box-office hit "The Host "(2006) and "D-War" (2007), a sci-fi monster flick by director Shim Hyeong-rae, which drew 3.19 million and 3.09 million, respectively, during the first six days of opening.
"The Thieves," if this trend continues, is expected to easily break the 5 million mark within this week.
During the same period, the movie raked in more than 50 percent of local box revenues, beating the Hollywood blockbuster "The Dark Knight Rises."
"The ticket sales for 'The Thieves' is showing a rare pattern, drawing larger audiences each day as time goes by," an official at the movie's distributor Showbox said.
Directed by Choe Dong-hoon, known for "Tazza: the High Rollers" and "The Big Swindle," "The Thieves" is about 10 South Korean and Chinese thieves teaming up to steal a valuable diamond necklace at a Macao casino.