I used the answer from this post:
http://superuser.com/questions/496845/how-to-have-num-lock-enabled-by-default-on-log-on-screen, it looks like is not a problem with the ASUS laptop but a problem with Win 8 on my case.
I tried the solution changing the value of "InitialKeyboardIndicators" key to 2 in any appearance on regedit. After that I went to Power options on Control Panel, then click on the left side: "Choose what the power buttons do", then I uncheck the option "Turn on fast startup " and restarted my laptop. It worked!!!
As I said, this happened to my on a laptop Asus ROG G751JT-CH71, using Windows 8.1 and with Windows Live login at logon screen, so please consider if your problem is on similar circunstances.