PHNOM Penh needs to invest in housing, infrastructure and roads in suburban areas of the city to avoid haphazard expansion, Chhay Rithisen, director of the Department of Urban Affairs, told a workshop in the capital Wednesday. According to a government master plan for urban development that runs until 2020, Russey Keo will be the focus of efforts to offer housing for the city’s expanding population. As many as 10,000 families come to live in Phnom Penh each year, Rithisen said, 90 percent of which could be absorbed by suburbs.