Bout's new lawyer had asked the Bangkok Criminal Court to push back the first plaintiff witness hearing to September 22, prosecutor Vipon Kititasnaisornchai told reporters.

"The lawyer, who recently took over the job from another, sent his representative to ask the court to postpone the hearing as he had already had another case scheduled today," Vipon said.

Bout, dubbed the "Merchant of Death" by the media, arrived at the court in orange prison garb, with his wrists and ankles shackled. He was arrested in a Bangkok hotel in a Thai-American sting operation after arriving from Moscow in March.

U.S. authorities have urged Bangkok to extradite Bout to New York, where he would stand trial for conspiracy to sell millions of dollars of weapons to Colombia's FARC rebels that they say could be used to kill Americans in Colombia.

U.S. prosecutors said in a statement Bout had been trafficking weapons since the 1990s, using a fleet of cargo planes to send arms to Africa, South America, the Middle East and elsewhere.

As a result of such activities in Liberia, the U.S. authorities froze Bout's assets in the United States in 2004 and banned U.S. nationals from having any business dealings with him, the prosecutors said.

According to the United Nations and the U.S. Treasury Department, Bout has sold or brokered arms that have also helped fuel wars in Afghanistan, Angola, Rwanda, Sierra Leone and Sudan.