St. Thomas wrote before the Enlightenment.

The Venerable Bede (673-735AD) taught that the world was round

https://www.gla.ac.uk/myglasgow/library/files/special/exhibns/month/jan2001.html

"Starting with the smallest units of time, the text describes days, weeks and months before proceeding on to lunar movements and the seasons; solar movements and years are then treated. The different lengths of days and nights and the variation of shadow lengths cast on the earth's surface at different times during the year are explained. Bede simply states that the reason for the unequal length of days is due to the globular shape of the earth, thus explaining the three-dimensional nature of the earth and refuting the notion that early medieval people believed that the earth was flat."

Bishop Virgilius of Salzburg (700-784AD) was alsop a global Earther;

https://virgilofsalzburg.com/telling-the-virgil-story/

There is an image shown on this site under which is:
"This composite image is used on the cover of the St. Virgil biography. The St. Virgil image is from the 1881 stained glass window In the Church of the Assumption, Morristown New Jersey. The globe represents Virgil’s mathematical commitment to the round earth with a circa-700 map of the world system of the Ravenesse geographer – one of the primary maps of Virgil’s era."

"Conclusion: Virgil was a thinker ahead of his time. He definitely taught that “the earth was spherical, and consequently a great portion of it was undiscovered, and that every nation had their Antipodes, or people living diametrically opposite of them” (Conyngham, p. 448)."

Hildegard of Bingen (1098-1179) was also a global Earther.

https://perthobservatory.com.au/ancient-astronomers/hildegard-von-bingen-1098-1179

"The earth, Hildegard maintained, was a sphere composed of the four elements—wind, fire, air, and water. Surrounded by layers of air and water, it was encased in an egg-shaped universe with an external “shell.”

https://books.google.ie/books?id=hdCTAgAAQBAJ&pg=PT150&lpg=PT150&dq=Hildegard+of+Bingen+(1098-1179)+and+the+shape+of+the+earth&source=bl&ots=M6cMXwFAib&sig=ACfU3U2oRSl4snGZjFOqA1kTt3JH65lKew&hl=en&sa=X&ved=2ahUKEwjBv-CsjZj1AhUChlwKHZdxChQQ6AF6BAgVEAM#v=onepage&q=Hildegard%20of%20Bingen%20(1098-1179)%20and%20the%20shape%20of%20the%20earth&f=false

Now what Flatearthers are INFERRING, that all these saints who held to a global Earth, and many others such as illustrated asbove, were undermining the bible and Catholicism with their global Earth conclusions.

No, we are explicitly saying that the modern cosmology is entirely false. Not that the saints are wrong (which, they certainly could be). The following is still technically a globe:

It is dishonest to insinuate that the problem St. Boniface had with Vergilius was about the rotundity of the earth, or that Pope Zachary condemned the concept of a global earth. The words of Pope Zachary were passed down in the Monumenta Germaniae Historica, just look them up, before again spreading misconceptions about Churchmen and Church history.

The Catholic Encyclopedia just says "a doctrine in regard to the rotundity of the earth".

The Monumenta are a compilation of primary sources.

I have Bl. Hildegard's The Divine Works coming in the mail, so I'm interested to read what she actually saw in her visions in her own words.

If I remember correctly, Hildegard mentions that the firmament turns on the four winds.  Not exactly a description of a globe, nor a space odyssey. I have the book somewhere, but I moved a few years ago and a lot of my stuff is still in boxes.  Guess I better see if I can dig them up.  Let us know when you get a chance to look at your book.