Marco where are you getting the fixtures from? I might go and watch a Nonthaburi game.
I use the page that Loko posted. The futsal coverage on Thai League Online is pretty good to be honest. Here is another link that might interest both of you: http://www.thailandfutsalleague.com/
The format is to have 3 games at the same venue on the same day, so if you've got a few hours to spare you could see a few games.