* Year's second major capital raising for Sea * Proceeds earmarked for strategic investment, acquisitions * Sea expands in new markets, to roll out Singapore digital bank * Almost five-fold surge in Sea shares in 2020 (Adds analyst's comment) By Scott Murdoch and Anshuman Daga HONG KONG, Sept 9 (Reuters) - E-commerce and gaming company Sea Ltd is looking to raise $6.3 billion in a share and convertible bond sale in Southeast Asia's largest ever capital raising, tapping growing investor interest in the region.