Bout, 41, faces several counts in the United States of "conspiracy to provide material support to a foreign terrorist organization" for purportedly arranging to sell and transport weapons, including portable surface-to-air missiles to the Revolutionary Armed Forces of Colombia, or FARC.
Lieutenant General Phongphan Chayaphan, chief of the Thai police's Crime Suppression Division, said Bout would remain in detention pending extradition hearings, which he estimated would take 60 days.
Bout's lawyer in Thailand, Lak Nitiwatanavichan, said he would fight extradition.
Bout, who has been called the "merchant of death," was arrested March 6 at a Bangkok hotel after a sting operation in which undercover U.S. agents pretended to be arms buyers from the Colombian rebels.
He could face 15 years in prison on the U.S. charge. Thai authorities had held him on a charge of using the country as a base to negotiate a weapons deal with terrorists, for which he could have been imprisoned for 10 years.
Regarded as one of the world's most wanted arms traffickers, Bout's purported list of customers since the early 1990s includes African dictators and warlords, including former Liberian President Charles Taylor, Libyan leader Moammar Gadhafi and both sides of the civil war in Angola. In the process, he has been accused of breaking several UN arms embargoes.
Bout, who was purportedly the model for the arms dealer portrayed by Nicolas Cage in the 2005 movie "Lord of War," has denied the current allegations against him and any criminal activities in the past.
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