THE biggest event on the Hong Kong judo calendar is heading for a more dramatic confrontation off the mat than on it. Officials are wrangling over who will take charge of the Hong Kong Open on Sunday at the Queen Elizabeth Stadium - a tournament which takes on added importance this year as it doubles as a selection trial for the upcoming world championships. ''We will be there on Sunday to take charge of the championships,'' says Lui Hon-wah, an executive committee member who has sided with a rebel group led by Wong Siu-ming trying to take control of the Hong Kong Judo Association. But Henry Shing Hing-yuen, chairman of the incumbent association, says: ''For the sake of producing a smooth running tournament, we cannot let them take charge. ''They are too hot-headed and don't think carefully before they carry out actions, otherwise they wouldn't be making such ridiculous demands.'' The latest twist in judo's power struggle comes after Lui and three other rebels - Chan Hung-wai, Wong Po-kee and Lee Chung-tai - took part in a mini coup on Friday, entering the association's offices at the Queen Elizabeth Stadium and telling the staff that they were now in charge of the sport. The four, along with Kan Wing-niang, are the only members of a 17-strong executive committee unanimously recognised as office bearers following the June 20 annual meeting. They were elected by both sides when an argument over eligibility of candidates ledto two separate elections being held. Both sides subsequently took court action. ''Until there is a court decision, the only people with the right to run the sport in Hong Kong should be the five of us,'' says Lui. ''Nobody else has the authority to organise open tournaments.'' The rebels won a Supreme Court ruling that there should be new elections for the 12 out of 17 places on the 1993-95 executive committee under dispute, but last week a court granted Shing's incumbent association the right to appeal. Lui, secretary of both the incumbent and rebel list of officers, said: ''According to the Supreme Court order, we five are presently the only members of the association's executive committee for the 1993-95 term.'' He says that this is why they seized control of the association's offices on Friday and told the two Sports Development Board-funded office staff to follow instructions from nobody else. ''We should be in charge of the daily operations of the association and we've told the staff they should report only to the five of us,'' said Lui. ''We've warned them not to listen to anybody else, and that otherwise they will be responsible for any losses to the association.'' The power struggle looks likely to come to a head on Sunday, with Shing saying: ''How could those people just walk in and take charge of an event which we had been organising right from the start? ''We welcome their assistance as they are members of our executive committee, but if they had wanted to help in the first place they should have attended our executive committee meeting on June 30.'' Shing's group have appointed Siu Tak-wong to take charge of the tournament and have already made all the preparations - from the arrangement of venue to processing of entries and deployment of staff. Shing said: ''How can five people claim to represent the executive committee when it is supposed to comprise 17 members? What they are doing is irrational, they do not follow the right channels and procedures. ''It was very wrong of them to go to the office and bother the staff, both of whom have been with the association for less than two months and are not involved in the dispute. ''Their actions are only causing more confusion in Hong Kong judo at a time when we should all calm down and sit together to find a solution to this bitter power struggle that is threatening to split our sport.'' Shing counters the rebels' claim that he and his supporters are illegitimate officials, saying that being the incumbent executives they should continue holding office until the present troubles are resolved. As for Sunday's competition, players will be hoping the wrangling does not prevent it going ahead. One event has already been a victim of the power struggle - last month's team championships which were boycotted by all but one club. In the meantime, Shing plans a meeting with the Hong Kong Judo Federation, a group who broke away from the association eight years ago in a similar power struggle. The federation had their own meeting last week and agreed, under certain terms, to reunification. But Lui said: ''What right has Shing got to call a meeting with them? ''We welcome the federation members back to the association but we have to settle our own differences before they can rejoin. ''When we won the court order for re-elections the judge said only the 52 existing clubs have voting rights, so if the federation rejoin us they cannot vote in the elections until the next ones in two years time.''