The Norwegian Royal Court confirmed today that Crown Prince Haakon will represent Norway at the funeral service and cremation ceremony for King Bhumibol Adulyadej (Rama IX) on 26 October 2017.
The death of King Bhumibol on 13 October 2016 has been marked by a one-year period of mourning. From the 25th to the 29th of October several ceremonies will take place. The actual cremation will be held on 26 October 2017, with many royals and other dignitaries in attendance. More details can be found among others on the Bangkok Post's Royal Cremation Ceremony page and Wikipedia.
Crown Prince Haakon will travel to Thailand alone. On the same day as the cremation ceremony takes place, his wife Crown Princess Mette-Marit will together with Princess Astrid Mrs. Ferner attend the gala dinner for the members of the Norwegian Parliament (Stortinget) hosted by King Harald and Queen Sonja.