Singapore was a great location. If a deal is struck, Singapore investors will flood into NK to locate businesses. There is a huge amount of Singaporean investment in Vietnam.
Sadly, all of this could have been over years ago if China had any real interest in regional stability. Instead they used NK as a mad dog on a thin leash, promising the west that they would try to control him, but warning that they couldn’t guarantee that he wouldn’t break loose. China is desperate for new lands on which to establish businesses, so it makes no economic sense that they didn’t force reform on NK. China kept NK poor and oppressed for strategic military purposes.