More than 500 other Cambodians have already been repatriated.
The three men were all facing deportation to Cambodia despite having served their sentences and living in the US as lawful permanent residents.
At the annual Overseas Khmer Summit (OKS), rights activists and academics in the Cambodian diaspora denounced the election and appealed to the international community to intervene.
The second annual Overseas Khmer Summit will focus on “unity, peace, continuity, and prosperity”.
The demonstrations marked the last push by the opposition to lobby for a boycott of the vote following the party’s dissolution by the Cambodian People’s Party-controlled Supreme Court in November.
Lawmakers tried again this week to push a bill that would protect some younger undocumented people in the United States.
Cambodian-American Chanda Choun Hopes His City’s Voters Give Him Chance to Serve.
Kosal Chhim was sentenced to five years in prison in 2001 for domestic violence and has now been sent back to the country he left as an infant.
Across the United States, there are nearly 2,000 Cambodian refugees facing deportation.
The family of a Cambodian-American jailed awaiting deportation last year are appealing the deportation order after a district court ruled his planned December deportation should be postponed. VOA Khmer's Men Kimseng reports.
In March, a group of Cambodians in Europe gathered to protest at the United Nations Human Rights Council office in Geneva, Switzerland, as the body was due to review human rights situation in Cambodia.