* Yahoo CEO Thompson apologizes to employees in email * Yahoo board expected to discuss internal review - source * Activist investor Loeb demands access to hiring records By Poornima Gupta and Alexei Oreskovic SAN FRANCISCO, May 7 (Reuters) - Yahoo Inc's board convened on Monday afternoon to discuss the mounting upset surrounding Chief Executive Scott Thompson, who has apologized to employees after being accused last week by activist investor Daniel Loeb of padding his resume, a source with knowledge of the matter said.