Thousands of Thais have gathered at Bangkok's royal palace for late-night vigils to mourn King Bhumibol Adulyadej, who died on Thursday.
His body was brought to the palace in a convoy as mourners lined the streets weeping. Millions watched live on TV.
Crown Prince Maha Vajiralongkorn has been named as successor, but has asked for a delay in the process. A regent has been appointed.
King Bhumibol was the world's longest-reigning monarch.
He had been ill for a long time and died on Thursday. Official mourning will last a year.
The cabinet declared Friday a government holiday, and flags are to fly at half-mast for the next 30 days.
People have been asked to wear black, and avoid "joyful events" during this period. Cinema screenings, concerts and sports events have been cancelled or postponed.
News websites have turned their pages black and white. All television channels in Thailand aired state media programmes including live coverage of the day's events.