JOHANNESBURG, Nov 9( Reuters)-The South African rand edged higher in early trade on Thursday, ahead of a speech by the Federal Reserve Chair that could provide insight on possible direction for U.S. interest rates.At 0638 GMT, the rand traded at 18. 4500 against the dollar, about 0.14% stronger than its previous close. The dollar was last up about 0.03% against a basket of global currencies. Fed Chair Jerome Powell will give a speech at 1900 GMT, which investors hope will hint at the future inte