The third ceremony will take place on Tuesday 7 November in Singapore.
But HELLO! understands that William and Kate's eldest child, Prince George, ten, is taking exams on the same week as the awards and the Princess wants to be at home to support him.
Kate joined William for the inaugural Earthshot Prize Awards at London's Alexandra Palace in 2021, when she brought back a lilac Jenny Packham gown for her green carpet appearance.
And in 2022, the Prince brought the Awards to Boston during his and Kate's three day visit last November.
The Princess was lauded for renting her green Solace London dress from Hurr.
It comes after the Prince of Wales's solo visit to New Yorkearlier this month to attend the Earthshot Prize Innovation Summit.
Speaking during a Q&A session at the event, which unveiled the 15 finalists for the 2023 Awards, the future king said: "As we’ve seen today, the Earthshot winners and the finalists bring that inspiration and optimism.
"And I think we’ve got to hang onto optimism and hope because it is the biggest driver of change, it is the biggest driver of innovation."
William added: "An important part of the Prize’s designs and development is not just to provide the solutions, but it’s the factor to make people believe there is hope, and there are people out there doing incredible things that will have a massive impact on our futures."
The Prince also travelled to Bordeaux for Wales's match against Fiji in the Rugby World Cup earlier this month, while the Princess watched England take on Argentina in Marseille.
In June, the couple attended the royal wedding of Crown Prince Hussein and Princess Rajwa in Amman, Jordan.
William and Kate, who share a close friendship with the Jordan royal family, attended the ceremony, as well as a glittering white-tie banquet.
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