* Additional funding to be mix of debt, equity (Recasts with more comments, industry context): SINGAPORE (Reuters) - Grab aims to raise another $2 billion this year as it ramps up expansion, its chief executive said, just weeks after announcing over $4.5 billion of funding in what has become Southeast Asia’s largest round of private financing. “We expect to raise $6.5 billion of total capital this year,” Anthony Tan said on Monday in an interview, in which he laid out Grab’s strategy to become an app-for-everything in Southeast Asia - home to about 650 million people.