Kwiatkowski, 32, recorded five assists in 18 games with Atlanta during the 2007-08 season and has played in 282 career NHL games with five teams. He played in Russia last season.
Krog, 33, had three points in 14 games with Atlanta in the 2006-07 season and had 86 points with Manitoba of the AHL last season. He has appeared in 202 career NHL games with five teams.
The Thrashers also signed unrestricted free agent goalies Drew MacIntyre and Peter Mannino on Monday.