AN alleged triad leader wanted by the Massachusetts District Court in connection with a gunfight in the United States fought extradition to America in Eastern Court yesterday. Stephen Tse Chun-on, 44, faces extradition on one count of conspiracy to murder arising from his alleged involvement in a shooting in Boston, Massachusetts, on December 29, 1988. Magistrate Fergal Sweeney fixed the hearing date for May 26. Tse was arrested at Lowu on January 6 with $150,000 cash and no luggage. According to Senior Crown Counsel Roger McMeans, who represented the US Government, Tse is the leader of a triad gang called Ping On or Kung Cheng. It was claimed that he discovered that two of the gang members had defected from the gang and made extortion demands from junior members. Payment of the demands was arranged in Tse's restaurant in Boston. Mr McMeans said Tse told one of his lieutenants to tell two other gang members to bring machine-guns. Tse then allegedly ordered other gang members to murder the two ''defectors'' with the guns brought to the restaurant. Both sides began firing but no one was seriously wounded. On a previous appearance in Eastern Court, Tse faced extradition on 12 counts, including one of conspiracy to murder in aid of racketeering in the United States.