Air Koryo certainly offers both Business Class (2-2 config) and Economy Class (3-3 Config). I am surprised that the question is asked how a communist airline could have separate seating class - there must have been tonnes of examples where airlines from communist countries have such distinction.
In case we forget, Vietnam (whose flag carrier is very progressive and has now joined the rank of B7E7 airlines) is still communist, and so is China, Russia, Mongolia, Cuba etc.
An Air Koryo IL
-62 was in BKK
on 29 Dec 2004 - the Pyongyang-Macau-Bangkok service was mostly not operated for many months, so I am not sure if this was indeed a resumption or just an ad-hoc charter. Prior to the suspension, the route was only operated when North Korean workers bound for the Middle East receive their visa approvals.
Flights from Pyongyang to Vladivostok, Khabarovsk, Shenyang and Beijing were deemed to be the main routes (according to Air Koryo officials in Sep 2003). Since the break-up of the Iron Curtain, traffic from communist European countries have evapourated.
My personal experience on Air Koryo (flying Biz class one way and Economy class the other - a conscious choice) was positive. Service wasn't as sophisticated as on other modern Asian airlines, but it certainly wasn't bad at all. Food was merely adequate and while the seats were not embellished with modern gizmos, there were fairly comfortable. The cabin does have a nostalgic feel to it. And the IL
-62M was pristinely maintained, both inside and outside.