*TEXT 025 01/04/63 PAGE 024 RED CHINA FIXING FRONTIERS RED CHINA PRODUCED A SECOND SURPRISE LAST WEEK . AT PEKING AIRPORT, PREMIER CHOU EN-LAI WELCOMED OUTER MONGOLIA'S PREMIER YUMZHAGIIN TSEDENBAL, 46, WHO IS NORMALLY REGARDED AS A RUSSIAN PUPPET . WHISKED OFF IN A BLACK, SOVIET-MADE LIMOUSINE AMONG CROWDS DUTIFULLY WAVING CHINESE AND MONGOLIAN FLAGS, TSEDENBAL WAS PUT THROUGH THE USUAL ROUTINE OF TOASTS, BANQUETS AND FULSOME SPEECHES . THEN, ON THE SAME DAY THAT RED CHINA ANNOUNCED PLANS TO DEFINE ITS BORDERS WITH PAKISTAN, TSEDENBAL AND CHOU EN-LAI SIGNED A TREATY FIXING THE 2,500-MILE FRONTIER BETWEEN THEIR TWO COUNTRIES . IT WAS ANOTHER LITTLE LESSON AIMED AT DELHI . AT THE FAREWELL BANQUET FOR TSEDENBAL, PREMIER CHOU EN-LAI SMOOTHLY NOTED THAT RED CHINA HAD NOW SOLVED ITS BORDER PROBLEMS ON THE BASIS OF " PEACEFUL COEXISTENCE " WITH BURMA, NEPAL, PAKISTAN AND OUTER MONGOLIA, MAKING THE POINT THAT ONLY TWO NEIGHBORS NOW REMAIN WITH WHOM CHINA HAS NOT MADE A BORDER ADJUSTMENT : INDIA AND THE SOVIET UNION .