DENVER, Aug. 16 -- An American man was arrested in Bangkok as a suspect in the 1996 death of JonBenet Ramsey, the 6-year-old girl from Boulder, Colo., whose unsolved killing became a media obsession, prosecutors said Wednesday. Local officials would not name the suspect, but two sources familiar with the arrest, including the lawyer for the Ramsey family, identified him as John Mark Karr, 41, a former schoolteacher who once lived in Conyers, Ga. .