The group was raising money to recruit a mercenary force and buy enough weapons to equip a small army, including anti-tank missiles and grenade launchers, prosecutors said.
"We're looking at conspiracy to murder thousands and thousands of people at one time," Assistant U.S. Attorney Bob Twiss said in federal court.
He said thousands of co-conspirators remain at large.
General Vang Pao, who immigrated to the United States in about 1975 and has been credited by thousands of Hmong refugees with helping them build new lives in the U.S., was accused of being the mastermind. He was charged with conspiracy to topple Laotian leaders.
Also charged was former California National Guard Lt. Col. Harrison Ulrich Jack, who was accused of acting as an arms broker and organizer.
Vang Pao had led CIA-backed Hmong forces in Laos in the 1960s and 1970s as a general in the Royal Army of Laos, while Jack is a 1968 West Point graduate who was involved in covert operations during the Vietnam War.
The attorneys for Vang Pao and Jack had no immediate comment after Monday's court proceeding.
Seven others, all prominent members of the Hmong community from California's Central Valley, also were charged, including Lo Thao of Sacramento County, president of United Hmong International, which the complaint says also is known as the Supreme Council of the Hmong 18 Clans; Youa True Vang of Fresno, founder of Fresno's Hmong International New Year; and Hue Vang, a former Clovis police officer.
Also charged were Lo Cha Thao of Clovis; Chong Yang Thao, a Fresno chiropractor; Seng Vue of Fresno and Chue Lo of Stockton, both of whom are clan representatives in United Hmong International.
U.S. Magistrate Judge Kimberly J. Mueller ordered all nine defendants to be held in custody until separate hearings later this week.
Contact information for the other defendants' lawyers was not immediately available.
The criminal complaint said Vang Pao, now 77, and the other Hmong defendants formed a committee "to evaluate the feasibility of conducting a military expedition or enterprise to engage in the overthrow of the existing government of Laos by violent means, including murder, assaults on both military and civilian officials of Laos and destruction of buildings and property."