(FILES) This file photo taken on May 14, 2018 shows Thai King Maha Vajiralongkorn presiding over the annual royal ploughing ceremony outside Bangkok&#039;s royal palace. - Thailand&#039;s King Maha Vajiralongkorn late February 8, 2019 said a move by a political party to make his sister Princess Ubolratana prime minister if they triumphed in upcoming elections was &quot;inappropriate and unconstitutional&quot;. (Photo by Panupong CHANGCHAI / THAI NEWS PIX / AFP)