Developments will include ''top-class hotels, luxurious shopping malls, office towers, entertainment venues, quality dining and chic nighttime hangouts.''
The group already owns or manages seven resorts across Phuket. Such a huge new investment can be seen as recognition of Phuket as an international-Thai island-city with tourism on its beaches and reefs.
It opens Phuket to further rapid development as a hub for the Asean region and for investment that extends beyond tourism.
According to the Bangkok Post, the development over seven years would put a shopping mall in Phuket's north, a resort and a mall in the ''western area'' with condos, and roll out the third phase of already-open Central Festival Phuket in Phuket City.
Announcement of the venture is likely to send other Phuket developers and retailers scrambling to revise plans and work out whether Central's ambitious project will affect them.
As one of the largest investors on the island, Central is clearly placing its faith in Phuket - even if the island still has unresolved issues with taxi standover thugs and ingrained corruption.
Tourism is inevitably subject to the vagaries of international economics and to fairly dramatic ups and downs. Phuket remains a one-trick tourist destination, attracting about three million overseas visitors in 2013.
Yet Tos Chirathivat, chief executive director of Central Retail Corporation, is quoted today as saying: ''As an outstanding tourist destination, Phuket's potential for long-term investment has caught the eye of Central Group.
''With an investment strategy conceived to transform Phuket into the dream destination for people all over the world, Central Group aims to fill all the gaps in the island's lifestyle business segment with high-end experiences that include top-class hotels, luxurious shopping malls, office towers, entertainment venues, quality dining and chic nighttime hangouts.
''The 20-billion baht investment, which will span a period of 5-7 years, will offer Phuket's visitors an unparallelled experience and support the government's policy to attract high-end tourists to the island.''
Central already has the large branded department store, Robinson department stores in Phuket City and Patong, HomeWorks, Power Buy, SuperSports, B@S and Tops stores on Phuket.
Seven resorts also dot Phuket under the Centara Grand, Centara Villa and Centara brands. At least one more Centara Grand is already being planned, south of Patong.
Given the size of Central's investment, one would hope their interpretation of Phuket's future promise is based on their own research, not the fake figures that are still being bandied about.
Latest unreal estimates put the number of visitors to Phuket above 11 million for 2013. Arrival and departure figures from Phuket international Airport cast doubts on that number.
With today's announcement coming from Bangkok, it's likely a more detailed explanation of plans will come on Phuket in the next few days.