Wiki shows the Vietnam losses of aircraft as the majority belonging to the 509th Fighter Interceptor Squadron (FIS) which was based at Clark AFB in the Philippines and belonging to Pacific Air Forces (PACAF), my guess it is a PACAF badge like this:
http://en.wikipedia.org/wiki/PACAF
The other loss was from the 64th FIS which was an Air Defense component from Paine Field, Washington which was TDY to South Vietnam in 1966 and their aircraft were painted in SEA colors so I'm guessing it is a PACAF badge.
WIP: Monogram 1/72 B-26 (Snaptite) as 73rd BS B-26, 40-1408, torpedo bomber attempt on Ryujo
Monogram 1/72 B-26 (Snaptite) as 22nd BG B-26, 7-Mile Drome, New Guinea
Minicraft 1/72 B-24D as LB-30, AL-613, "Tough Boy", 28th Composite Group