HONG KONG • It has been 18 years since Singaporean actress Michelle Saram first worked with Hong Kong star Louis Koo, on the 1999 action movie Bullets Over Summer.

Back on the big screen for the first time in about a decade, she plays his wife in a new film, Paradox, and has surprised him by looking exactly the same.

"Be it her appearance or her laugh, everything is the same," Koo tells Apple Daily.

Saram, 42, has shied away from the limelight after she married businessman Ajai Zecha, son of former Aman Resorts chairman Adrian Zecha, in 2010. In recent years, she has been going on business trips with her husband and taking care of his children from a previous marriage, she tells Apple Daily.

"They go to boarding schools," she says. "Because they're in different countries, I'll go to Scotland or Switzerland. I spend most of my time on a plane."

Directed by Wilson Yip and starring Koo, Paradox is the third movie in the SPL or Sha Po Lang action series, which started with SPL: Kill Zone in 2005.

Koo says he was wondering who could play his wife in Paradox when he saw a rerun of At The Threshold Of An Era II, the 2000 TVB drama he starred in with Saram. He thought he would ask her, and he was still in contact with her, he adds.

Saram, who has not been in a film since 2008 comedy Kung Fu Dunk, worried about acting again, but agreed to work with Koo after he assured her it would not be difficult.

"My first film was Bullets Over Summer, with Wilson Yip and Louis Koo," she says. The new movie is a reunion, she adds. "I was seeing old friends, I was happy."

•Paradox opens in Singapore on Thursday.