Bennie L. Thayer, a Kettering businessman who heads the Jesse Jackson-inspired Maryland Rainbow Coalition, said yesterday that he is "very seriously" considering challenging Rep. Steny Hoyer next year for his 5th District congressional seat.

"I have made up my mind to go for Steny," said Thayer, 46, who runs a convenience store. "The only question is whether I do it in 1986 or 1988."

Thayer's comments, during an interview, came after months of speculation in Prince George's County placed him in races for both county executive and County Council. Although he has never held elective office, Thayer, a Democrat, organized the statewide effort for Jackson's presidential bid last year and is credited with turning out the votes that gave Jackson a Prince George's win in the 1984 primary with 43 percent of the vote.

Thayer, who was to accompany Jackson on a Maryland swing through Prince George's and Anne Arundel counties today, said that he hopes to have Jackson's help in mounting any credible challenge against Hoyer, whose district encompasses most of Prince George's County's growing black population.

Hoyer, 46, a two-term Democratic incumbent, was originally elected to replace the ailing Gladys Spellman in 1981. He has said he plans to seek reelection next year.

A spokeswoman said yesterday that Hoyer had no comment.

Some political observers had expected Thayer to run for County Council member Jo Ann T. Bell's District Heights seat after he said earlier this year that he was no longer interested in challenging Hoyer.

"He really said that to you?" Bell responded when told of Thayer's comments. "There have been a number of rumors."

Wayne Curry, a politically active lawyer who is affiliated with the Rainbow Coalition, said Thayer's involvement would make for an "interesting contest."

"Thayer has demonstrated his ability to appeal to a broad range of people," Curry said.

State Sen. Decatur Trotter, the county's ranking black elected official, said he still plans to support Hoyer next year. Of Thayer's interest, he said: "It's a free country. Anybody has a right to run for anything he wants to run for."