His personal handwritten letter ("missilis") from February 1496 proves Rajki's literacy. Since the 1510s, Rajki involved as a lawyer in numerous lawsuits in different parts of the country, which fact confirms his professional status. For instance, he defended the interests of the Zagreb chapter against George of Brandenburg before the court of Petar Berislavić, Ban of Croatia in 1517. He represented Ladislaus Báthory of the Szaniszlófi branch during a long-time decades of lawsuit on the question of ownership over landholdings against some members of the Báthory of Somlyó and the Perényi families in 1519. The Szaniszlófis' defense team was initially led by another famous contemporary lawyer Gergely Makrai, and subsequently directed by Rajki, while Ferenc Fancsikai represented the Perényis. In 1523, Rajki defended Borbála, wife of the disgraced Ferenc Hédervári, Ban of Belgrade (who allegedly handed over the castle to the Ottomans without resistance), to prevent confiscation and distribution of the Hédervári lands among other relatives. Rajki also represented the Eger chapter and the Székesfehérvár Convent of the Knights of St. John of Jerusalem in 1519 and 1520, respectively.