They are ethnic Chinese Cambodian and Thai mercenaries known as Nungs. They were assigned primarily to CCN North(Command and Control North, 5th SF). They always went deep into Laos and Cambodia conducting recon of the Ho Chi Minh trail. They also were fierce volleyball players and seldom lost a match. We called it "combat volleyball". These guys went with US advisers into triple canopy jungle on "strings". I've got several hundred pictures of them (35mm slides) around here somewhere. They carried Grease guns and Carbines almost exclusively. Regards, Rick.
I flew gunship support for insertions and extractions for CCN in the late '60's early '70's out of Dong Ha (North of Quang Tri on the DMZ). Yes, we flew into many "interesting" places West of there, with "interesting" people. wearing "interesting" uniforms.