For him, the answer is yes, because thankfulness is "a special part of justice." Giving thanks to our benefactors, those who have given us a particular and personal favor, is an issue of obligation, or justice. We owe gratitude to them, and this is different from the related virtues of religion (owed to God), piety (owed to parents), and observance (owed to those who excel in dignity). We are left with thankfulness as a virtue distinct from these related excellences of character. Thankfulness is a matter of justice.
The point, I take it, is that Thomas believes that gratitude is important in a variety of ways, related to God, parents, excellent human beings, and finally those who have benefitted us via a favor of some sort. We owe something to all of these persons, and perhaps the upcoming holiday is a good day to at least partially seek to fulfill that obligation.