Mr Ngiam, 83, died on Thursday.
In a condolence letter addressed to Mr Ngiam’s wife Jeanette, Mr Lee called him a “versatile and outstanding civil servant” from the founding generation.
Mr Ngiam had spent 40 years in the apex Singapore Administrative Service where at 33, he became the youngest permanent secretary.
“Tong Dow also served on some of our most important statutory boards,” said Mr Lee, recounting how Mr Ngiam joined the Economic Development Board (EDB) in its earliest days and helped set Singapore on the path of industrialisation. “He worked tirelessly to woo investors and make Singapore more business-friendly.”
And as EDB chairman from 1975 to 1981, he helped Singapore move up the value chain into capital-intensive industries, and secure the country’s role as a regional business hub. “He also fostered a go-getting culture in EDB officers that persists even today,” Mr Lee said.
Mr Ngiam was the permanent secretary at the Ministry of Trade and Industry (MTI) when Mr Lee joined as Minister of State in 1984.
“As a young office holder, I benefited greatly from his considerable experience and sage advice.”
Mr Ngiam was on the economic committee Mr Lee chaired in 1985 that came up with recommendations to help Singapore recover from its first post-independence recession – one partly caused by a high-wage policy from the late 1970s which, together with an overvalued currency, chipped away at Singapore’s competitiveness.
“He worked closely with me to implement the recommendations and help our companies regain their competitiveness and recover,” added Mr Lee.
Many of the schemes introduced while he was the Housing Board’s chairman “stood the test of time and are still continuing today”, the PM noted, citing the Build-To-Order system and lift upgrading programme.
Another of his legacies is to be found in DBS Bank where he was chairman for eight years. He restructured it to sharpen its focus and expand into the region.
“His ethos of discipline and prudence continues to define the bank today,” Mr Lee said.
“His legacy will live on, and his contributions will touch the lives of many generations of Singaporeans to come,” he added.
Tributes also poured in from Emeritus Senior Minister Goh Chok Tong, friends and former colleagues.
ESM Goh, in a Facebook post on Thursday, described Mr Ngiam as Singapore’s economic czar. “When I was Prime Minister, I invited him for lunch occasionally as I found it worthwhile to listen to his views on Singapore’s economy,” he said.
Trade and Industry Minister Chan Chun Sing noted on Facebook that as the ministry’s first permanent secretary, Mr Ngiam was instrumental in shaping and implementing economic policies that catalysed Singapore’s transformation from Third World to First.
Mr Chan added: “We will continue to uphold his spirit of innovation and resilience as we chart our new path forward together.”
President Halimah Yacob, in her condolence letter to Mrs Ngiam, said his contributions continue to have an enduring impact on the lives of Singaporeans.
The President cited his key role in the birth of the MRT system, which he helped push to be set up despite strong opposition from some quarters in the Government. Mr Ngiam was permanent secretary of the then-Ministry of Communications.
“He was also a strong advocate for our local enterprises, which paved the way for the vibrant small and medium-sized enterprise landscape we see today in Singapore.”
Mr Ngiam was outspoken on issues such as the high concentration of scholarship holders in the civil service, and high ministerial pay.
Veteran diplomat Tommy Koh, a close friend who studied with him at Harvard University in 1963, called him a “loving critic of Singapore”.
He was also extremely thrifty, recalled Professor Koh.
“When he was the permanent secretary of the Ministry of Finance, I went to beg for more funding for the Singapore Symphony Orchestra.
“He said ‘no’, until I reminded him that it was established by his mentor, Dr Goh Keng Swee, and there is no leading city of the world without a resident orchestra.”
Mr Ngiam is survived by his wife Jeanette Gan Choon Neo, daughter Selina, son Kelvin, and three grandchildren.
Today, the wake at 4 Chestnut Avenue is between noon and 10pm, with a prayer service at 8pm. Tomorrow, the cortege will leave for Mandai Crematorium for a private service.