Investment plans that promise lucrative returns in a short time are often Ponzi schemes, where bonuses and monthly dividends are derived from newer members' cash infusion.

Home Affairs and Law Minister K. Shanmugam said last month that investment scam figures reported to the police from 2015 to last year doubled from 200 to 400, with more unregulated online investment platforms springing up.

Last year, the police Commercial Affairs Department received 142 reports from investors who lost a total of $7.8 million from trading on unlicensed platforms, up from 40 reports in 2016.

Such scams are also increasingly being peddled on social media by prominent influencers.

Financial blogger Dawn Cher, also known as SG Budget Babe, has seen more companies turning to social media influencers to sell investments.

"Social media influencers typically enjoy a fan following, where their followers tend to trust what they promote, and, when it comes to investments, this can be quite dangerous as the sum of money involved is typically not a small one," she said.

One retiree, who gave her name only as Madam Dora, found herself twice unlucky over dubious investments.

What started in 2012 as a $30,000 investment in a scheme giving discounts on flights, transportation and hotel stays, eventually transformed into a gold buy-back scheme.

Madam Dora was promised 323g of gold at the end of five years on top of her capital.

"It sounded like a good deal. But when it was time for me to collect my returns last year, I was shocked the office had been vacated. Even my investment agent had disappeared," said Madam Dora.

In 2015, a friend recommended she invest $7,000 in cryptocurrency.

She said: "My heart sank when a local newspaper report in November 2015 named the company in a US securities fraud investigation. I pulled out immediately."

The company returned only half her investment sum.

Today, the company has been placed under the Monetary Authority of Singapore Investor Alert List.