SINGAPORE (Reuters) - Thai billionaire Charoen Sirivadhanabhakdi's Thai Beverage is planning to spin off some regional beer assets in an initial public offering (IPO) that could raise as much as $3 billion (2.3 billion pounds), sources close to the matter said.The Singapore-listed company has approached banks about a listing of a unit that could house its beer assets in Vietnam and Thailand, one of the sources said on condition of anonymity because he was not authorised to speak to the media...