Lon Nol used the crisis to oust the Head of State , Cheng Heng .
Lon Nol took over the role himself , appointing the veteran anti-Sihanouk nationalist Son Ngoc Thanh as Prime Minister .
Lon Nol used the crisis to oust the Head of State , Cheng Heng , and took over the role himself , appointing the veteran anti-Sihanouk nationalist Son Ngoc Thanh as Prime Minister .