i am sorry.. i am from malaysia, and i do not speak thai.

i encounter the same problem, but i manage to solve it.

here is my guide.

http://www.haroldchia.com/2012/01/how-to-root-motorola-razr-after.html

first you have to downgrade your firmware using fastboot, then root it using doomlord, then use Vodoo’s OTA Rootkeeper to protect root, unroot.. then flash back, then update again will do the trick.