Once worth more than $30 billion (18.67 billion pounds) and listed as the world's eighth-richest man by Forbes Magazine, Batista says his debts now exceed his assets by $1 billion and the value of his remaining stakes in the oil, shipbuilding, mining and transportation companies he founded continues to shrink.

Batista also faces criminal and regulatory investigations into suspected insider trading and fraud.

On Monday, a judge ordered Batista, who has repeatedly denied any wrongdoing, to testify on Nov. 18, the first step in a legal saga that experts say could drag on for months, if not years.

At the hearing, he will be asked to explain his 2013 sale of 236 million reais ($98 million) of stock in OGX Petróleo e Gas Participacoes SA (>> Oleo e Gas Participacoes SA), his now-bankrupt oil company, as well as his failure to keep a promise to invest $1 billion in the collapsing venture. OGX's name has since been changed to Oleo e Gas Participacoes SA.

The judge who has agreed to hear the case has also frozen 1.5 billion reais in assets belonging to Batista and his family, a move that threatens to further crimp a lifestyle already stripped of its private jets, helicopters and speed boats.

Since filing for Latin America's largest-ever corporate bankruptcy last October, the once ubiquitous Batista has largely disappeared from the public eye, retreating to his mountainside mansion and the company of family, close aides and advisers.

Batista and his attorney Sergio Bermudes declined repeated interview requests.

"I was born a child of the middle class," Batista told the Folha de S.Paulo newspaper last month in his first public comments in nearly a year. "To return to that, it's something for me, you know, obviously it's a huge reversal for the family."

In Brazil, where many have gawked happily on social media as his EBX Group crumbled, those comments were widely ridiculed as a sign that Batista's period of enormous wealth and power had left him out of touch with the real world.

Batista responded with a series of tweets, his first in months, vowing his respect and understanding of the middle class.

Those were soon followed by rumours he had appointed the man responsible for his hair implants to the EBX board.

The rumour was proven false, but only after Batista fired off some defiant tweets that ended: "It's not true ... here's a fresh rumour: neither my masseuse or my dermatologist are being considered for any position on the board."

In his heyday as Brazil's best-known entrepreneur, Batista liked to boast that his businesses were "idiot proof" and that he would inevitably become the world's richest man.

When critics questioned claims that his ventures were a sure bet, he would laugh and shrug them off as envious naysayers.

His touchy replies to the recent barrage on social media has friends, associates and family members concerned, according to people who know him.

"Doesn't he realize it's time to shut up?," asked a person directly involved in Batista's affairs who declined to be named. "We all respect him, and he's working like crazy to salvage something from the mess, but it's always his mouth that gets him into trouble, you'd think he'd have learned."

JAIL TIME UNLIKELY

The hearing before a Rio de Janeiro federal judge next month will focus on what, how and when Batista told investors about share sales and investment promises. The insider trading case will partly turn on comments Batista allegedly made in May and June 2013 on Twitter championing OGX when the share price was plummeting and he was selling stock in the company.

Shortly after, OGX announced that it wouldn't be able to produce as much oil as expected from several offshore fields.

Batista has said that he was legally obliged to sell the stock to pay debts, not because he had lost confidence in the company. The court will also consider whether he knew or properly informed investors about studies showing difficulties with OGX's first oil fields when the company was declaring them commercially viable to regulators.

In addition, the judge will try to ascertain whether Batista and OGX were in the right when they decided not to honour a $1 billion investment pledge. Batista has said the collapse of his empire made it impossible for him to honour the pledge, and that he was misled about the true promise of OGX oil fields by company executives.

If convicted of insider trading and market manipulation, Batista could face one to five years in jail and fines up to three times the amount of any benefit he earned in his supposedly illicit actions. Prosecutors allege his actions cost investors 1.5 billion reais.

But jail time is extremely rare for first-time offenders in Brazil, especially those convicted of white-collar crimes.

The biggest risk Batista seems to face is to his reputation and pocketbook, since he looks sure to be tied up in costly litigation for years, legal experts said.

Meanwhile, Batista has been selling assets to pay debt. In August he moved to pay $2 billion to Mubadala Development Co PJSC by transferring 10.5 percent of port operator Prumo Logística SA (>> Prumo Logistica SA) and iron ore miner MMX Mineração e Metálicos SA (>> MMX Mineracao e Metalicos SA) to the Abu Dhabi government investment fund.

The restructuring of OGX is expected to be completed soon, after which his once controlling stake will drop to near zero.

His decline has also had a direct impact on his beloved hometown, Rio de Janeiro.

As Batista ran out of cash, he stopped funding community policing programs in Rio shanty towns, leaving police without part of their budget for equipment and undermining a programme credited with reducing crime.

He also pulled support for sewage projects designed to clean up Guanabara Bay and Rio's post-card lagoon, the venues for sailing and rowing at the 2016 Olympic Games. His private jets, now sold, are no longer available to organizers.

The renovations of the historic Hotel Gloria and Gloria Marina, both expected to be used in the Olympics, are stalled, and he has pulled out of a group that was slated to run Rio's storied soccer stadium, the Maracanã.

"It's easy to laugh at his troubles, but his decline isn't really funny," said Fernando Zilveti, a lawyer and finance professor at the Getulio Vargas Foundation in Sao Paulo. "He made lots of mistakes, but he also faced huge challenges."

(Editing by Todd Benson and Kieran Murray)

By Jeb Blount