A strikingly similar figure would be Avicenna, comparable in theological/philosophical influence.

Something striking to me is the similarities in their arguments for the existence of God; Avicenna's Proof of the Truthful, and Aquinas' Five Arguments (specifically the cause from contingency) are similar, though it's likely that Aquinas would have read Avicenna's proofs.

They are both also polymaths, and each studied a number of similar subjects of mathematics, astronomy, and medicines, though Avicenna's work outside of theology was much more influential and noted.

First time trying to answer so hope I did it right.

Wippel, J. F. (1990), “The Latin Avicenna as a Source for Thomas Aquinas's Metaphysics”, Freiburger Zeitschrift für Philosophie und Theologie 37: 65–72.

Pieper, Josef. A Guide to Thomas Aquinas. Trans. Richard and Clara Winston (San Francisco: Ignatius, 1991).

I'm going to have to disagree with /u/Pooflive about Avicenna. I would not by any means characterize Ibn Sina as remotely equivalent to Thomas Aquinas. Aquinas falls squarely within mainstream Christianity and his writings shape Catholicism to this day. Ibn Sina was branded a heretic by most Muslim theologians and his writings have little role in modern Islam. Some of the most influential Muslim theologians did not even accept Ibn Sina as a Muslim. It's not uncommon to see Ibn Sina described as a "devil" by later Muslim writers.

Ibn Sina is important, don't get me wrong, and you can't study the history of Islamic philosophical thought without reading and understanding Ibn Sina. His impact was historical, however, and has minimal impact in shaping Islam through the ages.

There are two philosophers/theologians I would posit fit your need for an "Aquinas equivalent" better. One is the 11th century theologian Abu Hamid al-Ghazali. The other is the 13th century theologian Taqi-ud-Din Ibn Taymiyyah. Interestingly, both considered Ibn Sina to be outside the pale of Islam, explicitly referring to him as a disbeliever.

Their writings were influential in their time, shaped Islam for centuries afterwards, and still have relevance to the modern Muslim. I can't think of any two Muslim philosophers who have had a bigger impact on Islamic theology through the ages than these two.

Neither of these are the most readable books the two wrote but I think if you're going to read just one book by each, these are the ones which best capture their ideas:

The Incoherence of the Philosophers of al-Ghazali, translated by Michael Marmura.

and

Ibn Taymiyya Against the Greek Logicians translated by Wael Hallaq (a translation of a famous summary of a larger work of his).