HM the King is the world's longest-reigning monarch.

Caretaker Prime Minister Thaksin Shinawatra, head of the executive branch, Supreme Court President Charnchai Likhitjittha, head of the judicial branch and caretaker Senate President Suchon Chaleekrua, head of the legislative branch, took part in the rehearsal at the Anantasamakhom Throne Hall, where the actual ceremony will take place on Friday.

Thaksin wore the gown of a Knight Grand Commander (second class, higher grade) of the most illustrious order of Chula Chom Klao - a royal decoration.

He invited members of th

e public to attend Friday's event. " We have prepared space around the Royal Plaza and Rajdamnoen Avenue for [the public]. We

have also installed giant screens there so that they can see His Majesty as he delivers his speech," he said.

Thaksin said the many royal guests who will arrive on Sunday would be welcomed by HRH Crown Prince Maha Vajiralongkorn and HRH Princess Maha Chakri Sirindhorn.

Meanwhile, the government is considering maintaining a permanent exhibition about HM the King, Government Spokesman Surapong Suebwonglee said. The exhibition at the Impact Convention Centre, which ends on Sunday, has drawn millions

of visitors from across the country.

"We have our choice of venue in mind already. It's in greater Bangkok," Surapong said.