Q: Is it possible to disable device's touch screen?

A: Yes, it's possible. In order to change this system behaviour the administrator must modify the script /usr/bin/X replacing the following command line

Xfbdev -ac -screen 240x320@90 -keybd keyboard,device=/dev/input/event1 -mouse tslib,,device=/dev/input/event0,rightbutton,samples=20,tolerance=4 -root-ppm /usr/share/pixmaps/xsplash-qvga.ppm

with the following

Xfbdev -ac -screen 240x320@90 -keybd keyboard,device=/dev/input/event1 -hide-cursor -root-ppm /usr/share/pixmaps/xsplash-qvga.ppm