Bout, wanted in the United States for allegedly selling arms to Islamic militants as well as South American and African war lords, has been held in a Thai jail since 2008 when he was arrested in a joint U.S. and Thai police sting operation.
Bout was arrested at a Bangkok hotel on charges of offering to sell several hundred Russian MANPAD anti-aircraft weapons to FBI agents posing as members of the Colombian militant group FARC. Bout denies the charges.
If sent to the United States, he faces several terrorism charges and a possible life sentence in prison.
But legal wrangling over his fate has kept the former Soviet air force navigator and translator -- he is said to speak six languages -- in a maximum security prison in Bangkok.
It was to the prison, rather than the United States, that Bout was returned after a brief visit to Thailand's Criminal Court to hear the latest ruling on his future.
The senior court rejected an application by the prosecution to drop new charges against Bout, 43, delaying again a potential extradition to the United States.
Bout's lawyers appealed an earlier lower court extradition ruling and lost that appeal in August. But in the meantime Washington filed further charges against Bout concerning money laundering and wire fraud.
The Thai Criminal Court is keeping him in the Bangkok jail pending a ruling, likely this week, on the new charges.
Bout's lawyers are likely to appeal the coming ruling should it come down in favor of extradition. Even if they lose the final appeal, Bout's lawyers could make a personal appeal to Thai Prime Minister Abhisit Vejjajiva, who has the formal authority to make the final decision.
"In accordance with the law, ultimately the executive has the power to decide but I would rather wait for the court ruling," Abhisit said last week.
Bout, who appeared in the Criminal Court wearing a bullet-proof vest and surrounded by police commandos, told reporters that he wouldn't receive a fair trial in the United States should he be extradited.
At the same time that Washington is fighting for Bout's extradition, Russian Foreign Minister Sergei Lavrov has expressed full support for him. In August, Lavrov said the lower Thai court ruling that would have allowed his extradition was "unlawful and political" above all else.
"I assure you that we will continue to do everything necessary to push for his return to his homeland," Lavrov said.
Bout, a large mustachioed man born in Dushanbe, Tajikistan, was nicknamed "Merchant of Death" by a former British foreign office minister.
But Bout claims he is innocent and simply in the transport business, having run his own aviation company since leaving the Soviet military. With help from his family and his wife, Bout claims to have purchased four Antonov-8 cargo aircraft that became the core and starting point of his aircraft fleet.
On the so-called Official Web site of Viktor Bout, he is described as "a dynamic, charismatic, spontaneous, well-dressed, well-spoken and highly energetic person."
"He is a born salesman with undying love for aviation and an eternal drive to succeed," the site says.
The site also praises Google for refusing an order by the U.S. government to block access to Bout's Web site as part of Washington's "political conspiracy" against him.