From the Dominican Breviary,
Exsultet Mentis, Vespers Hymn
Thomas Insignis, Matins Hymn
Lauda Mater, Lauds Hymn
There is also another Dominican Feast in Honour of St. Thomas with its own Hymns, Translation of St. Thomas
Another Office Hymn can be found in the Analecta Hymnica, Ortum Vitam et Exitum, Lauds Hymn.
Finally another ‘Hymn’ for St. Thomas, Pange Lingua (St.Thomas)