Several other additions are being developed for the resort, which is operated by Hong Kong-listed NagaCorp.
Developers also are looking to expand gambling in other parts of Cambodia, including near the southern beach resort of Sihanoukville and near what could be the biggest prize: Siem Reap, home to the Angkor Wat temple, Cambodia's most-renowned tourist attraction.
Government officials have blessed the idea of adding new casinos, despite protests from advocacy groups that worry that the projects will generate crime and push some residents off their land.
The government says casinos generated about $20 million in tax revenue last year, up 25% from the year before.
That revenue is helping Cambodia develop in such areas as education and health, said Phay Siphan, a spokesman for Cambodia's Council of Ministers.
The casinos also will encourage tourism, he said.