Some Victorian era philatelists would tell you, such kind of pictorials and FDCs are worthless. Well, the first official FDC is quite common, but not the second, it is a private FDC. The stamp set is tied by an authentic Phnom Penh Central Post Office (CPO) regular postmark, you can compare this with the fake private FDC I posted on 11th June, titled "Real First Day Collectables?".
In 1980s, Cambodians were still suffering from the after shock of Khmer Rouge terror. The country was closed off, the people were penniless. Basically no locals had spare time and dough for hobbies like stamp collecting. Only a very small number of foreigners, mostly aiders from the Soviet Bloc, would care about stamps as souvenirs.
I have tried to trace the premier owner of this private FDC, but failed. I acquired from a Singaporean private collector who bought from an Australian dealer. The clue stopped there.