That we have any Cambodian rock and roll music at all is, in and of itself, a minor miracle. The beautiful, raucous sounds of artists like Pan Ron, Sinn Sisamouth and the incredible Ros Sereysothea — one of the best singers of all time, bar none — ruled Cambodian culture in the late ’60s until the Khmer Rouge seized power, outlawing rock music and — horrifyingly — executing many of its biggest stars. That the music lasted is largely because it was squirreled away by Cambodian citizens, safe from discovery by the authorities. The forthcoming Rough Guide to Psychedelic Cambodia, out May 26, provides the perfect introduction to this ragged, joyful music. All of that spirit and energy comes through in the swinging “Paem Nas Sneha.” A surf-rock bassline charges beneath Pan Ron’s sweet, twisting voice, and the wiry guitar solo that appears halfway through makes it feel like the theme song to some late-night late ’60s spy film. It’s just one of countless treasures this brief musical movement produced.