A Vietnamese man accused of bilking a Chevy Chase businessman of $750,000 through an elaborate scheme of telephone calls and impersonations pleaded guilty in U.S. District Court yesterday to wire fraud and false pretenses.

Bang Thuy Bui, who lives in Vienna, Va., had claimed that he needed the money to pay taxes, fines and bribes to retrieve valuable assets he had stored in France after fleeing from Vietnam. According to court records, he told businessman Harvey Blumenthal he had a total of $5 million in cash, art work and precious metals in France.

According to court records, Bui told Blumenthal that he would reimburse him for the money, which Blumenthal paid out on 200 occasions; would let Blumenthal manage his assets when they were recovered, and would split any profits in joint ventures on an even basis.

Bui's lawyer, Thomas Abbenante, told Judge Louis F. Oberdorfer yesterday that Bui's story about assets in France was false. He said Bui spent most if not all the money obtained from Blumenthal at gambling casinos and race tracks in Atlantic City.

To back up his claims to Blumenthal, Bui, 44, repeatedly telephoned Blumenthal, pretending to be a variety of characters involved in his efforts to recoup his French assets. Among the roles he played were a French judge and a prosecutor, a customs official, a bank employe, a university professor, as well as Japanese and Australian investors allegedly interested in buying property Bui claimed to own on the French Riviera.

Bui, who is being held on a $50,000 bond, faces a maximum of eight years in jail and a $2,000 fine. Oberdorfer scheduled sentencing for March 26.