What you are doing is correct and should work. I would double-check to see if your file is
%album% - %singer% - %song%.tksns
or
%album% - %singer% - %song%.tksns
.txtIf you are not careful, Windows append ".txt" at the end and "hide" that extension so you thought you have a .tksns file but you actually have a ".txt" file.
It's probably easier to just download the file below and copy it to your H:\VIET KARAOKES\ folder. After downloading that file, restart TKaraoke. If that doesn't work, try clearing out all songs (File-->Clear Songs) and add folder H:\VIET KARAOKES\ into TKaraoke.
The differences between Pro and Free is
here.