Any info on that crossing?

I got 6 SETV visas and I'm getting ED in Savannakhet.

Is it safer to go through Nong Khai?

 

ED visa will be ready next day?

 

Also, any advice on buses from Khon Kaen to Mukdahan/Savannakhet?

Edited April 11, 20197 yr by Aburr

No problems are reported at that crossing.  You will be returning with a fresh Non-ED Visa, so even less reason for concern.

If your application is accepted, the visa is ready the next afternoon - but be aware they don't re-open until 2PM.  Be sure your school addresses the paperwork to the Savannakhet Consulate (not the Vientiane consulate).

I do not know the buses on that route, other than to suggest a VIP "3-seats-across" bus, for comfort (unless traveling with your partner).  If those are not available, look for Nakon Chai Air, which have the best 4-seat-across buses (IMO).