Events: Junior middleweight bout for the World Boxing Association championship (154-pound weight limit); welterweight bout for the WBA championship (147-pound weight limit). fifteen rounds or less.

Opponents: Champion Ayub Kalule of Copenhagen versus Sugar Ray Leonard of Palmer Park, Md., junior middleweights; Thomas Hearns of Detroit versus Bablo Baez of Los Angeles, welterweights.

Date: Thursday.

Site: Houston Astrodome.

Time: Premliminary bouts begin at 9 p.m. (EDT).

Sanctions: World Boxing Association and Texas State Athletic Commission.

Organizers: Top Rank Inc., Astrodome Championship Enterprises and PACE Management Corporation.

Estimated Purses: Leonard $2.5 million, Kalule $150,000, Hearns $1 million, Baez $100,000.

Television: Closed circuit only, seen in the Washington area at Capital Centre ($20 in advance, $25 the day of fight), and in Baltimore at Civic Center ($15 and $20 in advance, $25 the day of the fight).

Radio: Live on WMAL-AM 630 at approximately 10 p.m.

Astrodome Ticket Information: $300, $100, $60, $40 and $20. Information: (713) 799-9555.

Stadium Capacity: 52,000.

Preliminary Bouts: Beginning at 9 p.m. Tony ayala Jr., San Antonio versus Jerry Cheatham, Phoenix, junior middleweights, 10 rounds; jose (Pipino) Cuevas, Mexico City, versus Jorgen Hansen, Copenhagen, welterweights, 10 rounds.