The group was detained for around two weeks on charges of producing pornographic materials to promote the event at a private villa in the city flanking Cambodias famous Angkor Wat temple ruins.
Police, who broke up the party on January 25, initially accused the foreigners of "singing and dancing pornographically".
"The court has dropped charges against the nine foreigners released on bail. Only one British national will face trial," court spokesman Yin Srang told AFP, declining to elaborate.
All 10 defendants -- five Britons, two Canadians, a Norwegian, a New Zealander and a Dutch national -- had denied the allegations, saying that they were wearing "sexy" clothing but had not produced pornography, according to their lawyer.
While Cambodia teems with foreign tourists and boasts a rowdy nightlife, the Buddhist country is often strict when protecting local traditions or heritage sites.
Authorities banned skimpy clothing inside the Angkor Wat complex in 2016 and have previously arrested and deported foreigners for taking racy photos among the ruins, which are considered sacred.
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