Lenatai Victor Tamapua, a Samoan chief and member of parliament, said he planned to offer the title of 'Tui Taumeasina' to the monarch during a traditional ceremonial welcome to Charles and Queen Camilla on Thursday.
He will later lead Charles through a walkway on a mangrove reserve highlighting the impact of climate change on the Pacific nations and its communities.
"The king tide today is about twice that it was 20, 30 years ago, and that is affecting our land, and it's eating away at some of the areas that are so hard for us to control, and people (have to) move inwards, inland now," Tamapua said.
King Charles has spent a lifetime campaigning on environmental issues and in 2020 described global warming and climate change as the greatest threat that humanity has faced.
The offer of a high chief title for Charles comes after he was accused of "genocide" by an Australian Indigenous senator at Parliament House in Canberra during the monarch's six-day visit to Australia which concluded on Wednesday.
The Australian royal tour was Charles' inaugural visit to an overseas realm as sovereign, his first major foreign trip since being diagnosed with cancer, and the first visit by a British monarch to Australia in 13 years.
Charles is head of state in Australia, New Zealand and 12 other Commonwealth realms outside the United Kingdom, although the role is largely ceremonial.
He is also the symbolic head of the Commonwealth and is travelling to Samoa, his first to the island of around 200,000 people, for the Commonwealth Heads of Government Meeting. He is expected to leave Samoa on Saturday morning.
Over half of the Commonwealth's members are small states, many of them Pacific island nations facing the threat of rising sea levels caused by climate change. The leaders are expected to make a declaration on protecting the ocean, with climate change a key topic for discussion.
Britain has said it will not bring the issue of reparations for historical transatlantic slavery, demanded by Caribbean countries, to the table at CHOGM, but is open to engage with leaders who want to discuss it.
