PATTAYA, Thailand — A pair of self-described sex instructors from Belarus have been stuck in a Thai detention center for weeks. They say that they have evidence demonstrating Russian interference in the 2016 presidential campaign in the United States, and that they have offered it to the F.B.I. in exchange for a guarantee of their safety.

Their claim — that they are targets of a covert Russian operation to silence them because they know too much — might seem outlandish, but their case certainly includes some unusual circumstances.

They have influential enemies in Russia. They were arrested with the help of a “foreign spy,” according to the Thai police, and locked up on what is a fairly minor offense: working without a permit. And the F.B.I. tried to talk to the pair, suggesting that American investigators had not dismissed their account out of hand.

“They know we have more information,” one of the pair, Alexander Kirillov, 38, told The New York Times last month in an unauthorized phone call from the detention center, in Bangkok. Mr. Kirillov said his co-defendant, Anastasia Vashukevich, 27, had angered some powerful people. “They know she knows a lot,” he said. “And that’s why they made this case against us.”