The agency has tracked land prices in Surat Thani's Koh Samui district since 2011 and found they rose an average 35pc over the past four years, but only 2.4pc from 2011-12 due to an economic slowdown. Prices began to jump again in 2013.
The company predicted that prices could rise as much as 11.8pc this year, but might fall short of the forecast if the island is hit by a new bombing. A car bomb exploded in Central Festival Samui on April 10, injuring seven people.
The growth forecast did not factor in the bombing at the Chaweng beach mall, which is still under investigation.
Sopon Pornchokchai, the company's president, said land prices for five-rai plots along the beach road in Chaweng were B300,000 per square metre, or B120 million a rai, in 2015. In 2011, it was just B80 million a rai.
The Lands Department, however, still appraises the beachfront land at just B4 million a rai.
The second-most expensive land on Koh Samui is around Lamai beach at B70 million a rai and about B25 million a rai in Bophut, Chueng Mon and Mae Nam beaches.
The lowest price is about B15 million a rai on beaches such as Bang Kao, Pangka and Taling Ngam. But available land on those beach is difficult to find.
The area that has seen the biggest increase since 2011 is the Leam Yai area where the price has tripled to B15 million a rai.
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