He was the son of Boniface of Saluzzo and Maria di Torres of Sassari (in Sardinia).

Since his father died in 1212, he succeeded his grandfather Manfred II as marquess on the latter's death in 1215.

His paternal grandmother Azalaïs or Adelasia of Montferrat was regent during his minority until 1218.

[2] Manfred fought the expansionistic policies of Thomas, as had his father, and he defended the borders of his march with care.

He married in March 1233 to Beatrice, daughter of Amadeus IV, Count of Savoy.