Amy Cheng is trying to forget some of her lines for World-In-Theatre's restaging of Wife #11.

The play opening at The Arts House Play Den on Feb 26 chronicles 16 years of marriage in post-World War II Singapore, through written correspondence between husband and wife.

Director-playwright Desmond Sim wants his lead characters to retain the spirit of discovery while referring to the letters they hold.

"The thing is that after so many rehearsals, you naturally memorise the letters. I have to try to forget or at least remind myself to look at the lines," says Cheng, 46, whose acting credits include TV (Growing Up in the noughties) and film (Jack Neo's Just Follow Law in 2007).

In Wife #11, she plays the titular role opposite actor and Indian classical dancer Sonny Lim, who is also a founding member of World- In-Theatre, the 14-year-old troupe founded by nine theatre practitioners deeply influenced by the late director William Teo.

Lim is also assistant director (arts & culture) at Temasek Polytechnic, where Cheng is an adjunct lecturer. He roped her in two years ago for a private staging of Sim's play at the polytechnic.

Cheng had never seen the two-actor play before, but found herself identifying with the "steeliness" of the female lead in a time when women had fewer opportunities to be their own persons.

"The title shows there is no identity for the woman, she is purely a statistic. My impression of the male character was also not favourable," the mother of two says. "But I liked the character development. Nobody is completely a good person or completely bad either."

Wife #11 was first staged in 2009 with Casey Lim and Tan Kheng Hua, in a joint project between Action Theatre and the National Heritage Board.

Samantha Scott-Blackhall directed and Tan received a Life Theatre Award nomination in 2010 for best actress. (The award that year went to Wendy Kweh for her part in Singapore Repertory Theatre's Much Ado About Nothing.)

As part of the joint project, Sim had access to the National Archives. He was intrigued by a bundle of letters between a man and the sixth wife in his household.

"She wrote to him about mundane things, what was happening in the house with this wife or that child," says the 54-year-old. "Two generations ago, in my grandparents' time, polygamy wasn't so shocking. They took things in their stride."

Then came the Women's Charter of 1961, a landmark step forward for the rights of women, but which also would have shaken up polygamous households - as it does in Wife #11.

The restaging of Wife #11 is Sim's second recent outing as director and playwright after last year's Peranakan-themed play Pintu Pagar. It is a passion project for him and the two actors, who use some of their own furniture and clothes.

Cheng will wear a cheongsam she inherited from the first of her maternal grandfather's two wives. She considers the late woman her grandmother - she raised Cheng's mother, despite being of no blood relation.

"It was just a different time. My grandfather had two wives and he was considered modest," the actress says. She identifies with the character she plays - a convent- educated, English-speaking woman ahead of her time.

"It was very, very hard for women like that. They were given all this knowledge, but on the other hand, not allowed to live out what they were taught. But she adapted to it, just like women do today. We adapt."