AMERICAN INTERNATIONAL GROUP (New York) - Robert E. Lewis joined the company as vice president and chief credit officer. He will report to Edward E. Matthews, AIG vice chairman.

In the new position, Mr. Lewis will be responsible for setting worldwide policy on the extension of credit by all subsidiaries and divisions, establishing credit and risk management guidelines and identifying potential exposures, among other tasks.Mr. Lewis joins AIG from ING Bank in New York, the banking division of Internationale Nederlanden Group.

ARKWRIGHT MUTUAL INSURANCE CO. (Waltham, Mass.) - Wolfgang F. Friedel was elected senior vice president of marketing, sales and international operations.

Mr. Friedel, who joined the insurer in 1980, was previously vice president and manager for international operations. He has worked in a variety of positions, including regional sales manager and field sales manager. Previously, he was an account executive at Allendale Mutual Insurance in Los Angeles.

The insurance company also elected Carvie Thomas Freeman regional vice president and regional claims manager. He had been assistant vice president and regional claims manager since 1980. For the nine previous years he was a senior account executive for Arkwright.

Marilyn Dittman has been named regional claims manager of the insurance company's Hobbs Group Inc. subsidiary. She will be based at the insurance broker's San Mateo, Calif., office.

A claims manager since 1984 at American Business Insurance Brokers in San Francisco, Ms. Dittman served the previous two years at claims manager William C. Stapleton Insurance Agency in Aspen, Colo. She was also claims supervisor

from 1979 to 1981 at MIF Insurance Agency in San Francisco.