Bhumibol's only son, Prince Vajiralongkorn, was given the title "Somdej Phra Boroma Orasadhiraj Chao Fah Maha Vajiralongkorn Sayam Makutrajakuman" (Crown Prince of Siam) on 28 December 1972 and made heir apparent (องค์รัชทายาท) to the throne in accordance with the Palace Law on Succession of 1924 [REF].
Recent constitutions of Thailand have made the amendment of the Palace Law of Succession the sole prerogative of the reigning king.