Lyen was part of the team that investigated mass poisoning in Perak, Malaysia in 1991, did an anthropometric study of Singapore School children in 1991 and pubertal development in 1995. He was the founding president of two schools for disabled and autism spectrum disorder children, the Margaret Drive (1987) and the Balestier (1992) Special Schools. He helped establish The Rainbow Centre Singapore which manages both these schools, and trains special education teachers and parents of the students.
Lyen has co-authored and co-edited several books including Asian Child Care, and Rainbow Dreams. In addition, he has written and staged 20 musicals in Singapore, including: Big Bang!(1995): based on the life of Stephen Hawking, cosmologist. Orchard Square (1996): four teenagers work out their personal problems. Catch the Rainbow (1997): history of Singapore. Yum Sing! (1999): wedding flashback of how a bride and bridegroom met. Temptations (2000): cross-dressing TV cook show presenter falls for girl. Magic Paintbrush(2001): ancient Chinese folk tale. Song of the Whale (2002): story of Jonah and the whale. Sayang (2002): radio talkshow host and his fan, a lonely florist. Exodus(2003): story of Moses. Making The Grade (2004): Schoolmistress and her problem students. Blue Willow House (2006): About Lim Boon Keng and prostitutes in Singapore at the end of the 19th century. School House Rockz (2008): Television series musical about teenagers and their school problems. Monkey (2009): Puppet musical of an episode from Monkey: Journey to the West. It's Academic! (2011) love triangle among teenagers.