I learned previously here that the Khmer Rouge (and presumably the guerrillas who fought against the Vietnamese occupation of Cambodia weren't all Khmer Rouge) were dressed just like the Viet Cong, except for the use of krama scarves. What I wondered is, since they received weapons from the US and China, what kind they did receive, for I wondered if they might have also used US .30 and .50 caliber machine guns. I thought of equipping them with those to make them look less like Viet Cong.

they had as far as I know American .30cal WWII era
M1 Carbine
French sub machine gun
and Russian Ak's and other Russian weapons

Before the Khymer Rouge victory in 1975, corrupt Cambodian Army officers, officials, etc. sold tons of US equipment, including M-16's to the communist guerrillas (just as in Viet Nam) for a quick buck before deserting their country for the safer climes of the US. Sounds harsh, but it did happen.

It seems helmets were not as popular among Khymer Rouge as with the (communist) Vietnamese Army, although some troops are pictured wearing a type of tropical helmet, and, of course, the ubiquitous krama wrapped, or draped over the head. Khymer Rouge favored the soft hats made in China in which Chairman Mao is sometimes pictured wearing, and is the most common headgear. A less common alternative is a flattened conical straw hat. The rest of the uniform is usually Chinese issue dyed black.

You can see weapons used by Khmer rouge at the bottom of this link which says .30 and .50 caliber captured from goverment forces are used by them.

but I think the typical hat or krama wrapped on the head or over the hat will better identify it as a Khmer than a VC.

best regards

Thanks a bunch! Only I have to figure out where I can get these kinds of hats...

You can easily make it using putty or any sculpting material for the hat and plasticard or foil for the visor.

One other thing: I get the impression that the Viet Cong deliberately dressed themselves as farmers with the bamboo and bush hats they wore so they wouldn't be recognized as a fighting force until they readied their weapons. Same case with the Khmer Rouge while they were fighting the Vietnamese occupation of Cambodia?

In the early years of the Viet Cong they dressed like farmers because they were just that - farmers. Some were veterans of the Viet Minh, who fought for independence from the French in the early '50's. When that war was over and Ho Chi Min dissolved his guerilla forces, the fighters just drifted back to their homes and farms, some retaining their weapons, which were a mix of Chinese, Japanese, and captured French/US. In their beginnings, the Viet Cong were not the bad guys; after winning independence from France, had also to fight for justice and land and social reform from a corrupt dictatorship. Meanwhile, government (corrupt dictatorship) backed landowners demanded back rent as well as current rent (usually in rice) from their farmer tenants. (Remembering that under Japanese occupation the Japanese collected rice while the land owners remained in the provincial capitals, and then again rice cultivation and collection was disrupted during their war of independence). Viet Minh veterans (in the South) were viewed as local heroes and tried to negociate with land owners and their armed retainers on the farmer's behalfs. Push came to shove and finally armed confrontations with government troops, who usually came out second best. Diem (corrupt dictator and previous major crime boss and election rigger) saw this as an opportunity for US aid for his weak forces by claiming these guerrillas were communist infiltrators from the north, when actually their homes and farms were in the south. An escalating spiral ensued with the US supplying the South (huge waste) and North Vietnam and China supplying the now-called Viet Cong. History lesson over, VC guerrillas dressed they way they did because they were usually farmers by day and fighters by night and did not have uniforms. Later, with North Vietnamese aid also came communist indoctrination and political watchdogs.
As for Khymer Rouge, as far as I know, they always dressed in black-dyed Chinese issue uniforms and caps (sometimes with kramas and sometimes with straw hats, but the krama was an essential piece of Cambodian clothing and was and is almost always in evidence). The only reason I can think of why a Khymer Rouge in civilian clothing is because the Vietnamese were winning and the Khymer Rouge were busy running and trying not to be captured or killed.