The thing is, Malaysian's level of english vocab sucks hard.

OEM = original item manufactured by original factory, usually these oem items were customers set but were sent back for warranty / repair due to problem(s), so the company repaired them and now they are being resold as OEM with limited (usually 1 week) or no warranty at all.
Sometimes OEM items can be the original items bought the staffs of the company at a staff price, then resell them, also with limited warranty.

Typical Malaysians misuse the word OEM as fake but high quality item. Which is why i like to punch every sellers who sell fake items but called them as OEM.