His Majesty the King on Friday sent a gift of royal soil and a wreath to the funeral of Surin Pitsuwan.
The King's representative delivered the soil and the wreath to the house of the late foreign minister and Asean secretary-general in tambon Sai Ma of Nonthaburi's Muang district.
Her Royal Highness Princess Maha Chakri Sirindhorn, HRH Princess Chulabhorn and HRH Princess Soamsawali also sent wreaths of condolence to his house.
Surin, 68, died of a sudden heart attack on Thursday. Local and international figures and organisations, including the US government, have expressed condolences and paid tribute to him.
Mourners have flocked to his house to pay their last respects. They included former prime minister Chuan Leekpai, whom Surin worked for during his tenure at the Democrat Party.
Mr Chuan, who is the party's chief adviser, said Surin had set an example for others to follow by showing that an ordinary boy could rise to success on the national and international stages with diligence and determination.
The funeral ceremony was scheduled for 2.30pm at the Tha It Mosque in Pak Kret district, Nonthaburi.
Prime Minister Prayut Chan-o-cha assignd PM's Office Minister Suwaphan Tnyuvardhana to attend the ceremony.
