The acknowledgment was in line with Section 23 of the nullified 2007 charter, whose chapter about the monarch remains in effect.
This is what the relevant bit of Article 23 of that constitution states. That constitution was ditched by the 2014 coup and the junta, but maintaining sections related to the king (if that makes any sense):
In the case where the Throne becomes vacant and the King has already appointed His Heir to the Throne under the Palace Law on Succession, B.E. 2467, the Council of Ministers shall notify the President of the National Assembly. The President of the National Assembly shall then convoke the National Assembly for the acknowledgement thereof and shall invite such Heir to ascend the Throne and proclaim such Heir King.
Based on this, we guess that the prince now has to accept, and previously the rumors were that this would be on 1 December. But all of this is so convoluted, so secret and so make-it-up-on-the-go that we are really guessing.
Coronation comes later, after mourning is over. Kings of the past have often waited long periods before being officially and ceremonially crowned.
For the anti-democrat take on this, see the bizarre incantation by the “radicals” now royalists. The prince is already being remade as some kind of upright and gallant king. So the myth-making begins anew.
Update: The Nation has quickly gotten in on the rebranding: