Defender Thomas has been out for a month with a calf injury but returned to training this week, while winger Holmes is back to fitness after a niggling groin problem.
Rookie midfielder Ryan Doble is also back in training after a hip operation and could figure with Saints out of the play-off picture.
Full-back Graeme Murty (ankle) and midfielder Oscar Gobern (hip) are therefore the only injury absentees, while playmaker Morgan Schneiderlin serves the final game of his four-match suspension.
Youngsters Aaron Martin, Callum McNish and Alex Oxlade-Chamberlain could get run-outs as boss Alan Pardew begins planning for next season.
