In order to get to Nha Trang on time, we'd likely have to fly Thai Smile from BKK to SGN and connect to a Vietnam Airlines flights to CXR/Nha Trang from there. There should, in theory, be at least 4 hours in between these flights. My question, though, is about interlining baggage. It's hard to tell if Thai Smile (presumably under the guidelines of parent company Thai Airways) has an arrangement with Vietnam Airlines. Thai's interlining page directs you to a link on Vietnam Airlines' site that, of course, is broken.

I'd prefer not have to grab and re-check bags, if at all possible.

Looking for any first-hand advice. Thanks in advance!