The 24-year-old, better known by her stage name "Samson," made a final walk through the prison's grounds behind high-security walls to say farewell to her 1,245 fellow inmates.

"I couldn't sleep at all last night," she told reporters. "I feel reborn today."

Siriporn has served more than six years of her 10-year sentence for selling small amounts of narcotics.

She won early release when she beat Japan's Ayaka Miyano at the Klong Prem Central Prison in Bangkok on April 3, 2007 to clinch the World Boxing Council (WBC) female light flyweight title.

Prison authorities agreed to let her out early provided she reports to a parole officer every month until January 2009.

She will not be moving far away. Siriporn will now become a trainer for 27 boxers at the Women's Correctional Institute for Drug Addicts and will live in the warden's residence just beyond its walls on the outskirts of Bangkok.

"She is free to go anywhere without telling anyone," Thai prisons boss Nathee Chitsawang told reporters.

Siriporn said she was nervous about going into the capital, which has seen dramatic changes with a building boom in recent years.

"I know Bangkok has changed a lot and there are many experiences that I've missed out on, including taking the SkyTrain," she said, referring to the new light rail system.

She said she hopes to box for as long as she can, and then later to open a small restaurant.

She is expected to stage her first defence of the title in Thailand as early as July, WBC representative Choowong Toomkit said.

"I know being champion is difficult, but what more difficult is defending it," she said.

"Thailand loves a good fight: Thais flock to watch kick-boxing, Olympic boxing (the first sport in which the Kingdom struck gold at the Games) and even transvestite boxing -- one of the country's biggest celebrities is champion pugilist Parinya Charoenphol, who fought like a man to earn enough money to become a woman. Now, Thais have a new champion to celebrate: In April, a pint-sized woman named Siriporn Taweesuk, a.k.a. the Black Rose, did her homeland proud by pummelling her feisty Japanese opponent," The Time magazine reported earlier.

"She appears to be the first fighter to win a world title while behind bars," read the famed magazine.

Siriporn first learned boxing in her country's sports-mad Corrections Department three years ago in part to protect herself from more aggressive jail-mates. She also took prison courses in cooking, hairdressing and sewing, but none captured her imagination as much as boxing did.

However, Siriporn is not the first Thai to box her way out of jail. Two years ago, fellow inmate Wannee Chaisena faced another Japanese, Nanako Kikuchi, in the 2005 world straw-weight title bout. Like Siriporn, Wannee was in prison for dealing methamphetamine, or "crazy drug" as it's known in Thai. Unlike Siriporn, Wannee suffered a technical knockout. But the beaten fighter still managed an early exit from prison the following year, when Thailand's King Bhumibol Adulyadej pardoned her, along with three other female prison pugilists.

Before winning her world title, Siriporn harboured quiet hopes of opening up a convenience store after getting out of jail. Like many inmates, she must have worried about the threat of relapse. Now, Siriporn has told the press, her need for speed is gone. It has been replaced by the adrenaline rush of getting in the ring, as the Black Rose, and pummelling other women. A true Thai success story.