I once read a book called "Devil's Guard" that centers around this topic. How much truth is there to the claim that the French hired Nazis veterans post-WW2 to fight in their Vietnamese colonies?
Some did serve.
One of the missing (presumed dead) Legionairres who fought at Dien Bien Phu was Sergeant-Chief Bleyer, a veteran of the Grossdeutschland division of the Wehrmacht, who crops up several times at key points in the defence.
However, there wasn't large scale recruitment of entire units like in the Devil's Guard, rather individuals would join the Legion and be spread around the regiments.
Source: The Last Valley: Dien Bien Phu and the French Defeat in Vietnam by Martin Windrow.
If I may attach a question, did the French deliberately try to recruit German POWs into the FFL after WWII?