Neither player has been cleared for on-field drills but both can come off the PUP list at any time.
Michel, 24, missed practices last month after requiring a knee scope. He rushed for 931 yards and six touchdowns in his rookie campaign last season.
Thomas, who signed a one-year deal with the Patriots in April, is coming off a torn Achilles tendon. The 31-year-old finished last season with the Houston Texans after being traded from the Denver Broncos, posting 59 receptions for 677 yards and five touchdowns in 15 games.
New England did not place 2018 first-round pick Isaiah Wynn on either the active/PUP or active/non-football injury list, indicating his torn Achilles has passed a key recovery checkpoint, according to ESPN's Mike Reiss. The 23-year-old missed all of last season with the injury but is projected to be the team's starting left tackle in 2019.