Wearing a broad smile, T-shirt and warmup pants, the 32-year-old Briton was immediately taken to the airport, where security officers whisked him through passport control and put him on a commercial flight to London.
Leeson spent nearly 3 1/2 years at Tanah Merah prison, convicted of fraudulently hiding $1.4 billion in losses at Barings Bank.
His unauthorized futures trading made him one of the decade's most notorious white-collar criminals. The bad deals also led to the 1995 collapse of Barings and stunned dealers throughout Asia's then-booming markets.
The former trader, whose hair was noticeably thinning, underwent colon cancer surgery during his prison term, which was reduced by three years because of good behavior. Prison authorities said his cancer was in remission.
Now the subject of a book and film, Leeson has gained celebrity status. But his personality remains an enigma, his reputation an odd mix of loutish bravado and good-natured humility.
Leeson's wife Lisa Sims, 30, campaigned tirelessly after his arrest, trying to convince Britain and the world that her husband was not a heinous criminal. She later divorced him, however, after he published his book, Rogue Trader, revealing details of the couple's sex life.
Leeson, who failed math in high school, pushed his way into the financial world as a low-salaried clerk for Britain's dignified Coutts and Co. bank in 1985. He moved to U.S. bankers Morgan Stanley in 1987, and then to Barings in London in 1989.
Four years later, at age 26, he was paid $82,000 a year to toss around multimillion-dollar blocks of money from Barings' Singapore futures trading office.
He received huge bonuses, had a lavish apartment in Singapore's glittering Orchard Road district and frequented jazz bars popular among Singapore's affluent expatriates.
After his trading losses were discovered, he fled Singapore but was caught in Frankfurt, Germany, and brought back to the island republic, where a court sentenced him to 6 1/2 years in prison.
Leeson begins his new life with tight controls imposed by the High Court in London. He can't spend any money without giving two days' written notice to liquidators investigating the collapse of Barings Bank.
He's also can't profit from the film adaptation of his autobiography or selling his story to the news media. A $700,000 advance for the book has reportedly gone toward his legal bills.
The court allowed Leeson up to $7,900 per month for living costs, legal fees and health care. But accountants working for the Singapore-based liquidators must be given written, advance notice of where the cash has come from and exactly how it is being spent.
In addition, a Singapore law firm representig liquidators said it plans to keep investigating whether Leeson has any money hidden away from his Barings days.
His lawyer, Stephan Pollard, said Leeson would "certainly get a job as soon as is practicable" but cautioned that it would be difficult after spending time in prison.