This little shop is a common roadside occurrence throughout Cambodia and the greater Southeast Asia region in general. When it's not feasible to have a dedicated gas station with fuel pumps - improvise.
The bottle sizes are standard enough that you know how much petrol you're getting, although from looking at those 2L bottles, hard to say they're all filled equally. I saw plenty of motorcycles throughout my visits to SE Asia stopping at these kind of roadside stands to top off their tanks with another liter of gas.
I especially like the looks of those bottles on the 2nd row from the bottom. Are those whiskey bottles? Quite a luxurious choice of bottle for fuel, but let nothing go to waste.