Thousands of people are queuing up in the Sanam Luang area for an opportunity to pay their respects to the late HM King Bhumibol Adulyadej.
Long lines were seen from 4am on Sunday.
By noon, the lines stretched to several kilometres.
The late monarch reigned over Thailand for seven decades until his passing on October 13 last year. The grand Royal Cremation ceremonies for the late King are scheduled to take place in October.
An increasing number of Thais are visiting the Grand Palace, which is near Sanam Luang, to pay their final respects to the late monarch ahead of the cremation ceremonies.