While Operation Phoenix is/was fairly well known, the full scope (geographically and politically) has never really been shown. There were MANY of these clandestine ops going on, involving CIA/DIA, as well as army and "civilians" (ex-military, or military personel that had been temporarily removed from service and "sheep-dipped")...Many were conducted in Laos and Cambodia, even when we weren't supposed to be there. If you dig hard, under the freedom of information act, you can find tidbits about many of them, however all names have been replaced with numbers (or just redacted). According to the government this is because some of the people involved COULD be tried as war criminals, in some of the countries.
These operations continued way into the last years of the war, even after most of the US troops had been moved out.
Another interesting, similar, operation was called The Ravens ( or Operation Raven?). These guys (sheep-dipped US military) operated a LARGE forward air base, primarily for scouting, right in the middle of the Laotian jungle(with the cooperationof the local mountain tribes, who hated the NVA, or the communists in their own country. They still do today, and are still fighting. So the government pretty much, leaves them alone. There was actually a show on TV about it recently (and I was surprised at the amount of information that they were allowed to show.)
Don't ask how I know all this. My official records show that I was attending college in 1972-73, I've never been in the military, and I've never been to SE Asia. That's what the records show, and I'm sticking with it.