Are there risks of ED visa applications being denied if applied outside Laos?

ED visa applications possibly denied?

I've been in touch with 3-4 schools offering ED visas in Chiang Mai and Khon Kaen. All of them lay out the directions and process for getting the ED visa specifically through Laos. When I asked if other countries' embassies are OK, they say basically "yes, but we recommend Laos for its convenience." I don't know if they are referring to the overland convenience of travel there over, say, Cambodia or Malaysia or that other consulates are iffy. I have a trip to Cambodia coming up and my plan was to get the ED visa there. I'm wondering if the schools recommend Laos b/c it's just geographically easier or if other consulates sometimes deny EDs.