Success, said Tay, would depend on not just getting the physical infrastructure right but in elevating the mentality of the people. Tay advocated more civic engagement between policymakers, businesses and residents to chart the city-state's future.
"I hope that Singaporeans will look forward and outward rather than just grumbling about the here and now. We have become an exceptional city in a very dynamic region, and that is where both the challenges and the opportunities are," added Tay, who was also a three-term Nominated Member of the Singapore Parliament from 1997 to 2003.
As an ex-ambassador and frequent visitor to Singapore, Lavin also has faith in the future of the country but cautioned that its task ahead would not be easy.
"One of the cornerstones of Singapore's success is its market rationalism and economic promises," he said. There's been an enormous amount of work done in managing the integrity of this system but keeping this on track for the next 50 years is a challenge, he added.
Singapore's fortunes will also hinge on the political dynamics in the region, underlined by the rise of China, he added.
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"How China defines its role in the region and what other countries, including the U.S., think about that or do about that is really the political issue for the moment, and I think this will go on for years and decades," said Lavin, who left his life as the diplomat to set up his own e-commerce firm Export Now a few years ago.
Tay agreed that the next decade would be pivotal for U.S.-China relations, as the world's biggest economy headed toward presidential elections.
"As a friend of both countries, Singapore is in a sweet spot. We need to remain close to both if possible but not necessary by ourselves," he said. Instead, as part of ASEAN, Singapore could try and knit that group together, so it became an anchor for U.S.-China discussion, he suggested.
But as a smaller power, said Lavin, the country had to thread a fine line.
"Singapore to be as open as possible to all other powers to enhance its security," he said; if the U.S., Japan, India and other powers were active in the region, there was more room for Singapore to maneuver.
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"But if there is a unipolar movement then Singapore is at a disadvantage, because it just doesn't have the weight to push back against a unipolar situation," Lavin added.
Despite these challenges, the Singapore has potential to become a global city in Asia, the pair agreed.
The texture of the city has come to reflect a place that is everybody's kind of home or second home, for mainland Chinese, Indians, Japanese and other global citizens who come here for business, or residency, said Tay.
"In a way, being global, Asian and Singaporeans don't necessarily conflict. The order and sequence may change, some people might feel more Singaporean, less global, while others feel more global but still attached to Singapore; but I hope these three will have a real linkage," concluded Tay.
You can see more of this interview on CNBC's special report on Singapore's 50th anniversary "50 on the Dot" that plays out this weekend, starting August 8.