I wonder if his angle is to be taken in by North Korea in the hopes of being used as a poster child for North Korean propaganda. Considering he was on his way to getting flown back to the states for further disciplinary action after getting out of a Korean prison, he might assume that’s his best bet for a decent life since he might be assuming North Korea will pamper him so that they can use him to talk about how terrible the U.S. And South Korea are.
Back when I was in Korea, people that wound up in a Korean jail usually didn’t get shipped back to the states; it was more likely they’d be stripped of rank, locked down to the military base, and put on permanent detail for the rest of their time there (think "spending any free time scrubbing toilets and picking up trash around the base).
Things like serious assaults on local nationals could land someone a flight back though, so it’s very possible that whatever he did was bad enough that he thinks his life would be over if he went back to the states, so I guess that might be his play. How it’s going to pan out for him is another matter though - he may be treated well by the North Korean government (from what I’ve heard they tend to pamper their foreign mouthpieces to keep them placated and compliant), or he may wind up a bargaining chip for foreign aid from the U.S. depending on how low their resources are.
Mind you, I’m hardly an expert on the relations and current situation in North Korea, just a guy that was stationed over in South Korea for a few years in a non-intelligence capacity, so take all of this as idle speculation.
It only winds up being suicide by border guard if someone is trying to escape, not so much so if someone is trying to get in. Not too many people want to go to North Korea if they can help it.