A key member of a massive Thailand-based sex trafficking conspiracy pleaded guilty Tuesday to helping secure fraudulent visas for victims sent to Minnesota and elsewhere in a case first charged in 2016.

Sumalee Intarathong, who also goes by Alice Spencer Warren, pleaded guilty to conspiracy to commit sex trafficking and conspiracy to commit money laundering — more than one year after being extradited from Belgium to face charges.

According to Intarathong's plea agreement filed Tuesday, she was described as largely acting as a "visa application broker" for the organization. She and more than three dozen others were first charged in 2016 as part of an international probe dubbed "Bangkok Dark Nights."

Prosecutors have called the case an example of "modern day sex slavery," and five of the defendants were convicted after a six-week trial in 2018. Others have pleaded guilty since being charged.

"Ms. Intarathong worked directly with others at the highest levels in the organization to victimize hundreds of vulnerable women for her own financial gain," U.S. Attorney Andrew M. Luger said in a statement Tuesday.

Law enforcement once believed Intarathong was one of the "big bosses" in the organization. But in Tuesday's plea deal, federal prosecutors and Intarathong now agreed that was not the case.

"By pleading guilty today Ms. Intarathong took responsibility for her role in this conspiracy," said Aaron Morrison, Intarathong's attorney, in a statement Tuesday. "She looks forward to the opportunity to address the Court at sentencing."

According to Intarathong's plea agreement, the "large-scale international sex trafficking organization" that she took part in dated back to at least 2009. Thai women were made to travel to the United States to engage in commercial sex acts, and co-conspirators engaged in "widespread visa fraud" to bring the victims from overseas.

In Minnesota and other states the victims were kept in "houses of prostitution," which included apartments, houses and/or hotels. The victims were required to perform sex work to pay off "bondage debts" of between $40,000 and $60,000, which "far exceeded" actual expenses incurred by their traffickers. The ring targeted victims from impoverished backgrounds and deployed threats to make them follow through with paying off their debts.

"Until they paid off their bondage debt, the victims were effectively 'owned' and controlled by the organization," according to the plea agreement.

Intarathong studied and received degrees in industrial design and communications before coming to the United States, and her studies took her to Vienna and London, where prosecutors say she developed skills and experience to run a successful travel business. She became involved with the sex trafficking organization through connections in the United Kingdom, according to her plea agreement.

While in Thailand, she met with people who requested her help in preparing visa applications for victims to enter the United Kingdom and the United States. That included a woman known as "M" and a man known as "Tu," described as the leaders of a large sex trafficking organization. Investigators once believed Intarathong to be the leader known as "M."

Intarathong entered the United States in 2009 in San Francisco on a B1/B2 visitor visa with co-defendant Chabaprai Boonluea, whom the organization had trafficked to the United States to engage in commercial sex. She also arrived with Boonluea's "husband" from a sham marriage and the Thai trafficker known as "Tu."

Intarathong was later returned to Thailand and barred from returning to the United States after an interview with Customs and Border Protection while trying to re-enter the United States in July 2011. Back in Thailand, she continued to help the trafficking conspiracy with recruiting and preparing fraudulent visa applications for women being sent to the United States and Belgium.

Intarathong was first charged by criminal complaint in July 2016, and she was taken into custody the following month in Liege, Belgium. She was indicted in September 2016 and formally extradited in February 2021.

Intarathong on Tuesday admitted that the sex trafficking ring engaged in money laundering by moving the illegal proceeds from the United States to Thailand and directing victims to do the same.

"While the defendant did not engage in any sophisticated means herself, the defendant admits that the transactions were designed in whole and in part to conceal or disguise the nature, source, ownership and control of the proceeds of the specified unlawful conduct," the plea agreement reads.

According to the plea agreement, Intarathong's calculated guideline sentence range is between 19 and 24 years in prison. Senior Judge Donovan Frank has not yet scheduled a sentencing date.

Intarathong plans to ask Frank to reduce her sentence by about 4 ½ years to reflect the time she spent in custody in Belgium between August 2016 and February 2021. Prosecutors have said that they will defer to Frank on the request.

According to the plea agreement, federal prosecutors plan to ask that Intarathong be sentenced to 10 years in prison, citing sentences already imposed in the case.