MUMBAI • It has been a good year for Asia's richest man, Mr Mukesh Ambani.

The Indian tycoon added almost US$17 billion (S$23 billion) to his wealth as of Monday, the most in Asia, taking his net worth to about US$61 billion, according to the Bloomberg Billionaires Index.

In comparison, Alibaba Group founder Jack Ma's net worth grew US$11.3 billion, while Amazon chief executive officer Jeff Bezos lost US$13.2 billion.

The surge in Mr Ambani's fortune this year was fuelled by a 40 per cent jump in the shares of his Reliance Industries, a conglomerate that is pivoting more towards consumer offerings than its core oil refining and petrochemicals businesses.

The rally in the stock is more than double the gains for India's benchmark S&P BSE Sensex index during the period.

Investors are piling money on Reliance, betting that newer businesses such as telecommunications and retail could soon unlock value.

With a goal of building a local e-commerce giant to challenge the likes of Amazon.com in India, Mr Ambani has spent almost US$50 billion - mostly debt - on a wireless carrier that has become India's No. 1 within three years of its debut.

Mr Chakri Lokapriya, chief investment officer at TCG Asset Management which oversees US$3 billion in assets in Mumbai, said Mr Ambani "changed the narrative for Reliance Industries" as a leader not just in oil and gas, but also in telecoms and retail, and possibly soon in e-commerce as well.

"He successfully identified, invested and executed rapidly to create this new narrative," added Mr Lokapriya. "We believe this can potentially double shareholder value over the next four years."

Mr Ambani said in August that the newer businesses are likely to contribute 50 per cent of Reliance's earnings in a few years, up from about 32 per cent now.

While the success of the phone operator was a cause for cheer, the business mogul's plans to pare Reliance's debt has sent its stock soaring. Mr Ambani, 62, has vowed to slash the group's net debt to zero by early 2021. Plans include a stake sale in Reliance's oil-to-chemicals business to Saudi oil giant Aramco, listings of the telecoms and retail units within five years, sale of tower assets and strategic partners for a digital platform linked to Reliance Jio Infocomm, the phone company.

The value of Reliance's shares has almost tripled since the end of 2016, when Jio entered the Indian market with free calls and cheap data and forced some heavily indebted incumbents to exit or merge with rivals.

With more than 350 million users, unlisted Jio reported a net income of 9.96 billion rupees (S$190 million) for the September quarter, while the other two private-sector operators amassed record losses.

Still, investors have been wary of the ballooning debt at the group that spent about US$76 billion in the last five years.

Reliance Industries had a net debt of 1.54 trillion rupees at the end of March, Mr Ambani told shareholders in August.

The proposed transaction with Aramco has run into a hurdle, threatening Mr Ambani's debt paring plans. An Indian court has sought details of Reliance's assets after the Indian government petitioned to stop the proposed sale in an unrelated arbitration lawsuit.

Mr Ambani, however, has a proven record in keeping his promises that investors are relying on.