* Real estate attractive investment asset class for rich Asians. : HONG KONG/SINGAPORE, June 28 (Reuters) - Some foreign wealth managers are scrapping plans to open offices in Hong Kong in favour of Singapore, as the rich begin to move funds from the Chinese territory where a new extradition bill has stoked public unrest, people familiar with the matter said. A mid-sized European private wealth advisory firm has abandoned a plan to set up its Asia arm in Hong Kong and will instead aim to launch it in Singapore, its London-based chief executive told Reuters.