When I was stationed at Nakhon Phanom , Thailand in 67-68, I'd see the T-28s sitting on the apron , but I remember them as being all black, no gray underside.
I think they just come to NKP to have major maintenance performed, because I never saw them bombed up, just sitting with empty racks.
You'd see black aircraft flying out during broad daylight, probably going back to Laos.
They took their Raven nickname seriously , some of the pilots worn black flight suits.
Black aircraft, black flight suits, hot hot sun, had to be miserable.
Some of the pilots were westerners, bigger guys, but most looked small physiques, Laotian or Thai.
We were told they were CIA. But there was also a lot of BS floating around, never knew what to believe .
One time the apron got buzzed by a diamond of black T-28s, the back guy of the formation was upside down.
I wasn't privy to whatever the repercussions were to that stunt, If they really were CIA , then likely nothing .
I was driving a truck pulling a trailer loaded with napalm bombs to the flight line when this happened, with my attention divided, I about put it all in a ditch.