Khailee Ng has a keen nose for spotting promising start-ups.

As a managing partner for venture capital firm 500 Startups, he is tasked with identifying and helping cultivate some of the businesses of the future.

And he has advice for would-be founders hoping to build the next big thing: Look beyond the top segment of society.

Too often, start-ups focus on creating products and services for wealthy consumers in advanced economies, Ng said. But there are many important — and potentially lucrative — problems to be solved in poorer, developing economies.

"I don't think a lot of people think about that," Ng told CNBC Make It. "You can actually make a lot of money by serving a population which doesn't have that much money."

A start-up strategy for Asia

Indeed, that is where Ng, who is part of the Silicon Valley firm's Southeast Asia office, focuses much of his funding.

The investor was one of the early backers of now multibillion-dollar Indonesian e-commerce marketplace Bukalapak, which provides technology for the country's traditional, family-owned street stalls.

His teams' other regional investments include Singapore-based ride-hailing unicorn Grab and Malaysian on-demand work platform GoGet. Unicorns are technology start-ups valued at $1 billion or more.

As such, Ng encouraged aspiring entrepreneurs to look at developing markets with a long-term view and consider some of the wider trends that are likely to occur.

"I want to encourage entrepreneurs to look at any of their markets, especially if they're looking at large markets like Indonesia and Southeast Asia broadly, (and) think of the bigger picture and the longer horizon," advised Ng.

500 Startups, for instance, when looking at potential investments, considers the relationship between consumption, productivity and gross domestic product in a given market and how that will evolve. More sophisticated markets tend to be productivity-focused while developing countries remain consumption-led, he said.

"The first wave of large unicorns, a lot of them are very consumption-centric. But later on, when a lot of people are oversaturated with consumption points, you try to think about productivity," he said.

Those metrics can help a start-up determine the wants and needs of a particular market, Ng continued.

"Thinking along those lenses, I definitely think Southeast Asia has stepped into a new phase now, where building start-ups which fall into increasing people's productivity (will) be the next wave," he said. "I look forward to seeing more entrepreneurs actually build more companies that can serve the broader populations."

A 'once-in-a-lifetime' opportunity

Ng is not alone in his mentality.

Speaking at Singapore Fintech Festival late last year, the founder of multibillion-dollar Indian financial technology company Paytm advised aspiring entrepreneurs to focus on building products and services for users in developing markets, rather than already well-served advanced economies.

"It is a once-in-a-lifetime opportunity for entrepreneurs to build this in this side of the region," said Vijay Shekhar Sharma, noting that many advanced economies are already saturated.

"The next five billion customers in the world will be served using the technologies and the methodologies that are built in Asia," he predicted.

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