This sounds like you're looking for a dubbed version or Khmer-language localization for the 2012 Chinese historical drama, The Qin Empire II: Alliance (大秦帝国之纵横).

អាណាចក្រឃិន ២៖ បទពិសោធន៍នៃការនិយាយខ្មែរ

Narrator: "From the studios that brought you history’s greatest dramas... comes the sequel to the legendary saga."

This series is the second installment in a larger epic based on the novels by Sun Haohui