A proposed offshore wind power project in Vietnam could have total capacity of 3.4 gigawatts and require investments of $11.9 billion, according to one of the developers, setting it on course to be the world’s biggest.

The Ke Ga project offshore Binh Thuan province will be developed in 600-megawatt phases, according to a statement from Singapore-based Enterprize Energy Group Dec. 7. It will make use of 9.5 megawatt wind turbines initially, though more powerful ones are expected over time, according to the statement.

Project financing will be led by Societe Generale SA, said Ian Hatton, chairman of Enterprize Energy in...