WASHINGTON (AFP) - He is looking to revolutionise transportation, colonise space and develop implantable brain-computer interfaces.

But along with Mr Elon Musk's grand ambition comes a brash demeanour with little tolerance for criticism.

The founder and chief executive of Tesla and other companies now faces securities fraud charges over a tweet which regulators said misled investors about taking the electric automaker private.

The charges come with Mr Musk facing increased scrutiny over his volatile behaviour that has included smoking marijuana during a podcast interview and assailing a Briton involved in the Thailand cave rescue as a "pedo guy".

Mr Musk built the widely admired auto-manufacturer with global ambitions Tesla, along with the private space exploration firm SpaceX, the brain-computer interface start-up Neuralink, and Boring Company - designed to build tunnels that could transform mass transportation.

This month, SpaceX said it would send Japanese billionaire Yusaku Maezawa to fly around the moon as early as 2023.

But Mr Musk's eccentric behaviour has fuelled concerns in recent months over his ability to manage his vast empire.

"At times, Musk appears to be working against himself," analyst Gene Munster of Loup Ventures wrote in a research note this month.

Mr Musk has lashed out at analysts during quarterly conference calls as "boring" and criticised the media for scrutinising his actions.

A week ago, a British caver who helped in the dramatic rescue of 12 boys trapped in Thailand earlier this year sued Mr Musk for calling him a "pedo guy" and a "child rapist".

The defamation suit filed in Los Angeles by Mr Vernon Unsworth, a Briton involved in several cave rescues, follows a highly public spat between the two after Mr Musk travelled to Thailand and offered to assist in rescue efforts.

Still, the 47-year-old South African-born Musk is recognised as one of the most influential innovators in the United States, and has an estimated net worth of more than US$20 billion (S$27.3 billion).

Mr Musk's conduct has drawn comparisons to United States President Donald Trump, another prominent figure who has embraced filter-free social media and whose mental stability has been questioned.

And like Mr Trump, Mr Musk has lambasted the media and been picky about appearances, granting a few rare interviews to publications like the Wall Street Journal, while favouring Rolling Stone magazine.

Mr Musk has suggested the sceptical coverage of the company stemmed from the media's dependence on advertising from the oil and conventional car industry.

He has discussed creating a website to "rate the core truth of any article" that would be called Pravda.

Regardless of his reputation, Mr Musk, who has frequented the Metropolitan Museum of Art's annual gala, among other glitzy appearances, has seen his wealth soar with Tesla after earlier ventures.

After leaving South Africa, Mr Musk, who holds US and Canadian nationalities, completed academic work in Ontario and the University of Pennsylvania.

By 25, he had created Zip2, an online advertising platform, and was a millionaire by age 30 after selling the company to Compaq Computer in 1999.

He followed that with the creation of the online bank X.com, which was later merged into PayPal and bought by eBay for US$1.5 billion in 2002.

He also manages a foundation focused on education, renewable energy and paediatric health.

Mr Musk has also had a stormy personal life, having been divorced three times - twice from the same woman - and has five living sons.