Fansubs translated from the Thai DVD by AdisornP are available from Subscene (from a 720p version, but that was an upscale). Some errors but not too many glaring ones, although it can be hard to tell what might've gotten lost in the translation. I just watched this and there's no Girls with Guns content until an hour and fifteen minutes in, and very little even then, so don't bother seeing it for that.
Wise Kwai's review
The actors are good and I wanted to like this movie more than I did. Unfortunately, it has a very leisurely pace, little action of any kind, and little payoff for sitting through the dry spells. The saving grace is the humor--there a few very funny moments. I was expecting it from the trailer, but I wasn't expecting it to be dragged out for far more than it was worth, to the point of foot-shuffling discomfort, and to have worn out its welcome well before the end. The film badly needed tighter editing and more substantive content to fill out the running time. "I get it. That was funny. Can we move on to the next scene now? I've finished laughing; I don't need any more time to catch my breath." It is unbelievable how much time Saturday Killer devotes to the main character's various erectile dysfunctions; it really starts to feel like the main plot of the film at times. Will the main character ever succeed in getting his man-parts to work right? I'm on the edge of my seat. Someone took what should have been comic relief, plot device, and a metaphor for character development and decided it should be an end in itself. There's even a scene of someone urinating on the main character's face, which seems appropriate to describe the level of care and consideration that went into this storyline and, to some extent, the attitude of the film in general.
Ultimately, it just seems like a silly and empty exercise with no real exploration of character backgrounds or motivations, rather like a documentary revisiting moments from other movies in the genre with a laid back, rambling host with no real point of view who just keeps bringing up random stuff and not knowing where to go with it. Apparently this was intended as a parody, which is always a good catch-all for criticism, but if you haven't seen the specific things its parodying, you can't help but take many things seriously, and those parts will fall flat or leave a negative impression. Also, movies that are wholly parody and don't attempt to also be movies unto themselves are seldom worth spending an hour and a half on. Hopefully, the other 2 parts of the trilogy, Sunday Killer and Friday Killer (intended to be more serious), will be better.