I had just remove and reinstall both memory. That do the trick..so problem solved. Thanks😀

Do you think I should go back to Windows 8 to see if it hardware problem?

I can confirmed it is x550d..cant found alot about it online..maybe this model only for my region?
But if the ram work fine before, then it shouldnt be hardware problem right?
FYI I did use...

The retail ram was 4 gb
Then I installed another 4 gb. The motherboard has 2 ram slot, that time im on Windows 8. It work fine(with +-7.5 GB usable)
The issue came when I install win10
I also...

i'd just fresh install win10 pro 64bit and my only 3.21gb of ram usable out of 8gb..
im using windows 8 before and not having this problem.
im using asus x550d
Processor AMD A10-5750M APU with...