I’ve found some images of the B-307s used by the International Control Commission in Indochina. They belonged to the French firm Aigle-Azure and had French Registrations F-BELU and F-BELV. If you go to this site and then click on the registrations for B-307, you can get the data on owners and fates and some photos.
AeroTransport Data Bank (ATDB) - Index 8B - Aircraft Registrations
Other French registered B-307s were F-BELX and F-BELY
Here are some more sites with additional (in some cases conflicting) information:
This site, which deals primarily with the Smithsonian B-307, has a list of B-307 crashes that indicates that B-307s flew under French, Cambodian, and Laotian registrations (some of the aircraft may have served under more than one registration):F-BHHR (Aigle Azur Extreme Orient), F-BELZ (Airnautic), F-BELV (one of the ICC aircraft), XW-PGR (Royal Air Lao), XW-TFR (Cambodia Air Commercial), and XW-TFP (Royal Air Lao)
The Strange Truth About the 28 March 2002 Boeing 307 Crash
Here is a Royal Air Laos advertisement image:
Air Laos
This Time Magazine article mentions that the aircraft belonged to Aigle Azur:
How Not to Supervise a Peace - TIME
Here is a report on the crash of F-BELV in November 1965 with the loss of all on board:
~MIAs~
Here is a report of sightings of F-BELY and F-BELX that (apparently erroneously) refers to them as the ICC aircraft:
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Don