My prediction - it would not be delivered on a missile. Probably a boat.
Or a submarine. That is possible, and in fact they need to test a sub-delivered H bomb at some point.
It's likely that their previous accident in NK destroyed their testing site so that's why they are selecting the Pacific.
After it becomes obvious that the UN can't or won't do anything about NK (other than ineffective sanctions), The US, SK, and Japan should start seriously planning a strike. preferably non-nuclear. The enemy is the NK regime, not the people.