Hi Wanna,
The White Stem is a different species to Huperzia foliosa but I am not sure what the white stems botanic name is. Genetically the white stem is related to Huperzia phyllantha. Could be Huperzia pachystachyon? or Huperzia elmeri? Not sure. I also have the same white stem from the Philippines and from Sabah and Borneo but your plant from Cambodia is much prettier.
regards
Ash