TOKYO, Feb 9 (Reuters) - For years, SoftBank Group splashed out billions on startups at near-peak valuations without batting an eye. Now founder Masayoshi Son's tech powerhouse is relying on a new weapon as it searches for the next big thing in AI: caution.

The strategy marks a vast turnaround for a company that completely transformed the world of tech investing with its high-conviction bets on startups at an unheard of scale.

It also highlights the lingering effect of SoftBank's "defence mode", a strategy it adopted after being hit by plummeting valuations in the aftermath of the pandemic, when higher interest rates eroded investor appetite for risk.

"We're being very prudent when we look at these opportunities out there," Navneet Govil, the chief financial officer of Softbank's investment arm, the Vision Fund, told Reuters in an interview late on Thursday.

"We're financial investors not strategic investors."

The Vision Fund unit made just 29 new and follow-on investments in all of 2023 out of more than 300 companies it studied.

The October-to-December quarter was the unit's most miserly since 2017, with SoftBank saying the funds made $100 million in new investments, a drop from the heady days of 2021, when they spent $20.9 billion in April-June alone.

"It's a good approach. Given the difficult period they went through, they've become very strict on choosing investees," said Mitsunobu Tsuruo, an equity analyst at Citi who covers SoftBank.

On Thursday, SoftBank reported its first profit in five quarters, and a $4 billion investment gain at the Vision Fund business.

Its war chest has ballooned to 4.4 trillion yen ($29 billion) in cash, cash equivalents and liquid bonds, it said.

Even before the runaway success of chip design firm Arm , in which it owns around 90% and which listed in New York in September last year, SoftBank said it was exclusively focused on investing in artificial intelligence (AI).

Arm's share price surged more than 55% on Thursday, powered by forecasts of robust demand for its technology to design chips for AI features.

SoftBank CFO Yoshimitsu Goto said on Thursday Arm would soon be indispensable to AI and has previously called the chip designer "the core of the core" of SoftBank's group of companies.

EARLY INNINGS

Potential investments could be in AI hardware, infrastructure or applications, Govil said.

"We're still in the early innings of a fast-growing space. These disruptors can easily by disrupted by other disruptors."

Companies will need to meet strict criteria about their "transformative" quality and capacity for AI innovation, product market fit and scalability, unit economics, and track record of execution, Govil added.

But when it comes to AI, SoftBank has a mixed track record.

Although CEO Son has touted the promise of AI as an investment opportunity for some years, the vast majority of the more than 400 companies currently in the portfolio have not seen their valuations rise despite the excitement surrounding AI and AI-related companies over the past year.

"There aren't many winners in the AI market," said Amir Anvarzadeh of Asymmetric Advisors.

Valuations have shot up for companies seen as direct beneficiaries of a rise in AI-related applications, such as chip maker Nvidia. That means there will be fewer, if any, companies that can meet SoftBank's more stringent criteria.

"Everyone's on top of this. The ship has sailed," Anvarzadeh said.

While Son has made some bad bets on companies, such as now bankrupt office-sharing business WeWork, he's also backed some big winners including AliBaba, Arm and mobile internet technology, so it may yet be too early to rule him out of further AI gains.

"There's also a high chance that they'll make an extremely large, controlling stake investment," Citi's Tsuruo said.

"They would need to make sure they have the dry powder for it." ($1 = 149.3600 yen) (Reporting by Anton Bridge; Editing by David Dolan and Miral Fahmy)