Heart Beat Saigon is my weekly option for a night out with full of out-of-the-world excitement. Their location varies in different exotic places in Saigon and If you follow their news on Facebook, you are actually be taken from surprises to surprises. :) The expat scene can be seen throughout their events and is good if you want to immerse in the expat crowd of Saigon (which I know is super friendly and casual). Their drinks depend on the location they rent and mostly is cheap and affordable.
Now, for the music, the event organizer is one of the most experienced in terms of partying, got a taste for good electro music, and have a wide connections to DJs worldwide. I have came to their events and danced to music of European as well as Asian DJs. So, this complex of music sometimes make a newcomer (especially locals) feel strange, and that they have better check out the DJ styles before coming to the show (otherwise be shocked if you like). Haha.