One of nicest looking salon I've ever seen in Phnom Penh is de Gran. Run by Japanese stylists, it offers the best of what beauty expertise Japan is known for. I haven't tried their services yet since I usually don't fuss too much about my hair. A trip to the local barber is enough but I'd probably try it out when I'm in the mood to change my current undercut style. If you're in Phnom Penh check it out, info here.