To show the tablet keyboard start this process :
C:\Program Files\Common Files\microsoft shared\ink\TabTip.exe
However, since Windows 10 Anniversary update, you need to turn on in Settings the option of "Show Touch Keyboard in Desktop Mode when No Keyboard Attached".
This can be achieved by running this .reg file:
Windows Registry Editor Version 5.00 [HKEY_CURRENT_USER\Software\Microsoft\TabletTip\1.7] "EnableDesktopModeAutoInvoke"=dword:00000001