Veteran Guiding leaders credit her with helping to raise funds for the movement when funding was scarce, and with helping to secure a plot of land for the Guiding headquarters in the Clemenceau area in the 1960s.
She says she supported the movement because she believed in its values, which she felt were especially relevant during Singapore's formative years.
"It was about how to bring up girls to be good citizens, to never think about race, to help one another. That was exactly what all of us needed," says the mother of three children, grandmother of 10 and great-grandmother of 12.
Even after her husband died in office in 1970, she has continued to support the movement, for example, by accepting invitations for dinners and fund-raising events.
"From time to time, I will help them because we are friends," says Puan Noor Aishah, who has an award for Brownies and Guides named after her, and is a recipient of the Laurel Leaf award for distinguished service to the movement.
The Guiding movement also remains in the heart of former Girl Guide, Ms Chua Sock Koong, 59, group CEO of Singtel. She says Guiding has helped her in her career.
"I'd like to think the Guides motto - Be Prepared - has somehow stayed with me all these years."
Training in her youth helped in Everest feat
The foundations for the mental and physical resilience that Ms Lee Li Hui needed to climb Mount Everest was laid when she was a Girl Guide.
She says: "Guiding laid the foundation for making one more confident in the outdoors."
Ms Lee, 35, was the first Singapore woman to reach the peak of Mount Everest, the world's highest mountain at 8,848m, in 2009. She was part of the Singapore Women's Everest Team, the first all-female expedition from Singapore to scale the summit.
Training on a demanding schedule for five years before their feat was a mental challenge because they did not know if they would be selected from an initial team of 28 members, says Ms Lee, a product innovation manager in the reinsurance industry.
The training took place most days of the week and included climbing a 30-storey HDB block several times, carrying backpacks weighing about 20kg, with 5kg ankle weights strapped on.
On the mountain, steely nerves were also needed to keep climbing in minus 40 deg C conditions, where "one's toes and fingers were always cold to the point of pain", she says.
The expedition team was whittled down to six members, five of whom made it to the top of Everest. One team member did not because of illness.
Ms Lee, who is married to a 36-year-old professional in the oil and gas industry, has been drawn to outdoor challenges since her youth. In 2013, she crossed 560km of Greenland in icy conditions on skis, a feat she accomplished with her friend, Ms Jane Lee, who led the all-woman Everest expedition.
Since Everest, Ms Lee Li Hui has also climbed to the summit of Aconcagua in Argentina, the highest peak in South America, in 2011.
Ms Lee, who has no children, recalls meeting her fellow guides frequently after school ended to plan annual campfires and other activities.
"I remember soaking firewood in kerosene, which is no longer the practice now. We had splinters in our hands and it made us feel rugged," she says with a smile.
"When you're mountaineering, you put your life in the hands of one another. Towards the end of the Everest climb, it was the commitment to the team goal that drove me. It was not letting others down."
• Commemorative stamps featuring four prominent women associated with Guiding will be sold at the Singapore Botanic Gardens gift shops on Saturday and thereafter at the Guide Shop, 9 Bishan Street 14. The stamps include wartime heroine Elizabeth Choy; President Yusof Ishak's widow, Puan Noor Aishah; Brigadier-General Gan Siow Huang; and mountaineer Lee Li Hui. For online orders, go to www.girlguides.org.sg.
Correction note: In our earlier story, we said that Aconcagua in Argentina is the world's second-highest peak after Everest. This is incorrect. We apologise for the error.