I tried duckduckgoing it for quite a bit and failed. Does anybody have an idea?
Terrot 500 RGSTA ?
Peugeot 175 D4 ?
From this forum (en français bien sûr). It speak about motorbike since 1950, so that would make sense with Indochine and I think I can recognise some of the models from archive photos. It says that before 1950, French army used a bunch of brands like BMW, Harley, Triumph, Gnome et Rhone and others from 1930 and WWII, but from 1950 and onwards they tried to harmonise the material and the list is on the forum.
Otherwise, your best bet would be searching for CEFEO material (corps expéditionnaire français en Extrême-Orient) as it was the more involved in the war.
There is a book about material used in this war but I don’t know if they wrote anything about motorbikes.
The forum from the first link seems to be a good source of information tho.