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)