[1] He was sent to Rome in early 1303, alongside other prelates with the leadership of Stephen, the Archbishop of Kalocsa, to represent the interests of Charles against the rival claimant Wenceslaus.

There Wenceslaus II of Bohemia called upon Archbishop Michael Bő to crown his namesake son as king, but he refused the threat.

[3] According to a document, Thomas only recently returned to Hungary from his visit to the papal court, which reinforces the assumption that his election was a mere formality and was appointed to office by Pope Clement V himself.

Wenceslaus who had succeeded his father in Bohemia renounced his claim to Hungary in favor of Otto III, Duke of Bavaria on 9 October 1305.

According to his promissory note (obligatio) from February 1306, he had to pay 2,000 golden florins as his servitium commune and ten servitia minuta to the Roman Curia.

[8] Thomas borrowed money in 1307 to repair the cathedral, but renovation works lasted for decades, surpassing his archiepiscopal tenure.

Thomas called all the subjects of the realm to obey the king's commandments, otherwise he was ready to place the whole kingdom under interdict and launch a crusade against the treacherous barons.

[9] After Charles' partisans occupied Buda in June 1307, Thomas captured and imprisoned those local pro-Wenceslaus clergymen, who even excommunicated Pope Benedict XI prior to that.

[6] The archbishop presided that general diet in the presence of Gentile in the Dominican monastery of Pest on 27 November 1308, which elected Charles king.

In preparation for the coronation, they also urged the Transylvanian oligarch Ladislaus Kán, who captured Otto, to hand over the Holy Crown to Charles, but he refused to do so.

Thereafter Thomas, alongside Amadeus Aba and Dominic Rátót, negotiated with the voivode in Szeged on 8 April 1310, on the conditions of return of the crown.

He surprisingly laid siege Buda in June 1311, then Charles sent an army to invade Matthew Csák's domains in September, but it achieved nothing.

The oligarch threatened to besiege Esztergom in the spring of 1312; as Charles I dealt with the neutralization of the Aba dominion, Thomas was forced to ask for peace from Matthew and abandoned most of the claims for damages in early March.

[15] Thereafter Thomas resided in Lőcse (today Levoča, Slovakia) until January 1312, where he negotiated with the Abas about the transfer of three castles in Szepesség (Spiš) region.

Alongside other lords and prelates, Thomas participated with his banderium in the royal campaign, which consisted of successful sieges and the decisive Battle of Rozgony in the summer of 1312.

There lying on his deathbed, an elderly baron and soldier Egidius Monoszló made his final testament at the local Franciscan friary, and Thomas presented the document on 11 March.

[17] At the turn of 1311 and 1312, Thomas refused to confirm the election of Nicholas, the provost of Dömös as the new Bishop of Vác, alleging procedural irregularities.

After Charles neglected to reclaim Church property that Matthew Csák had seized by force, the prelates of the realm – archbishops Thomas, Ladislaus Jánki and their eleven suffragans – made an alliance in early 1318 against all who would jeopardize their interests.