I’ve never been to Cambodia, so I really don’t know, but I assume you’ve seen the post here.
When I was there they were using green papaya in lieu of the Vietnamese pickled daikon, but it seems like they are now using cabbage slaw. They also used a chili-spiced mayo. And the fillings weren’t more Cambodian than an imitation of traditional Vietnamese fillings.
The Cambodian places listed here http://www.movetocambodia.com/phnom-penh/cambodian-sandwich-face-off-nompang-versus-banh-mi-bros/ seem to share more in common with Vietnamese meat fillings, including the classic deli meats version.
The NYC version http://www.numpangnyc.com/menus/ shares use of chili mayo and lack of daikon with Siem Reap.
