If I'm not mistaken, the Thai throne is vacant right now. It's the President of the National Assembly who will invite the Crown Prince to become King of Thailand. I don't know however if it is possible to choose another candidate.

Have you seen the Crown Prince's full name BTW? It is: Vajiralongkorn Barommachakkrayadisonsantatiwongse Deveshrathamrongsubariban Abhikhunuprakarnmahittaladuladej Bhumibholnaresvarangkura Kittisirisomburana Savangavadhana Barommakhattiyarajakumara

Quite impressive if you ask me