Its a Coach award seat. U on KE is coach award and D is biz award.

As far as the seats go themselves, coach on KE isn't bad, better than coach on NW for certain. You probably won't have AVOD or much else for entertainment, but on NW 744's you wouldn't have that anyway. Overall your experience should be better than if you did NW PVG-NRT-BKK. If you have very much of a layover then ICN is much better than the Skyteam section of NRT for shopping and other things to do.