The Pacific island of Tonga was Friday preparing to bid farewell its late King George Tupou V, rehearsing the funeral procession and declaring two public holidays to coincide with the mourning.

The body of the 63-year-old king, who died in Hong Kong this week, will arrive in the capital Nuku'alofa on a Chinese charter aircraft on Monday, then lie in state in the royal palace for a day before his burial.

Tuesday's funeral is expected to be a grand affair, with the late king's body carried from the palace on an ornate platform by 150 people to the royal tombs where Tongan monarchs have been laid to rest since 1893.

"On the occasion of the state funeral of His Majesty King George Tupou V, Tonga will declare 26-27 March a national public holiday," the government said in a statement.

Businesses, offices, bars and nightclubs are set to close until after the funeral, the Ministry of Information and Communications said from Nuku'alofa, where buildings have been swathed in the mourning colours of black and purple.

The funeral and burial ceremonies will be traditional, with Lauaki, the Chiefly Undertaker, already in Hong Kong to ensure proper protocol is observed, the government said.

A royal vigil will be held on the evening of the king's arrival back in the Throne Room at the palace, where his body will lie in state until the funeral ceremony begins.

The king's funeral was moved forward a day to Tuesday, March 27, at the request of his younger brother and successor King Tupou VI, his country's high commissioner to Australia.

The South Pacific nation has declared an official period of mourning until June 19 for the dead monarch, remembered as an eccentric who brought democracy to his impoverished nation.

The Ministry of Tourism said the mourning ceremonies would mark a special moment in history, with Tongans dressing in black and wearing traditional woven ta'ovala mats.

"While it is an incredibly sad time for Tongans around the world, there is a real beauty in the way the country comes together to celebrate the life of such a well-loved and respected monarch," acting director Sandra Fifita said.