Inspired by what was done in China, Beschi adopted the native Tamilians' lifestyle in his life and in his missionary work. For example, he adopted the saffron coloured robe generally worn by a sannyasi. He visited several important centres such as Tirunelveli, Ramanathapuram, Thanjavur and, of course, Madurai to learn the Tamil language. He met with persecution in 1714–15 and escaped a death sentence. This gave him more time to master the Tamil language in which he soon showed great proficiency. During the first six years, he worked as a missionary in Elakurichy, a town near Tiruvaiyaru. Then he served as parish priest in Kamanayakkanpatti, one of the oldest mission centres in Tamil Nadu. He worked in the Thanjavur area till 1738 and settled in 1740 on the Coromandel coast where he remained till the end of his life. He helped build the Poondi Matha Basilica at Poondi near Thanjavur, Vyagula Matha Church at Thanjavur, The Perianayagi Madha Shrine, Konankuppam at Mugasaparur in Konankuppam, and Adaikala Maadha Shrine at Elakurichi. These churches are now Catholic pilgrim centres. He died at Ambalakaadu in Thrissur, Kingdom of Cochin, and is buried at Sampaloor, where his tomb can be seen. Robert Caldwell, one of the eminent Tamil liguistics and historians, in his book 'A Political and General History of Tinnevelly in the Presidency of Madras: From the Earliest Period to the Cession to the English Government in AD 1801' opines that, based on the writings of his biographer and the letters written to Europe at the same time, "It is certain from authentic records that Beschi was "Rector" of Manapar in 1744 and that he died there in 1746. This was in the 66th year of his age and the 40th of his residence in India. It is very probable that Manapar was the first place in the Tamil country where Beschi resided after he left Goa, in consequence of which he might naturally wish to end his days there." He, in the same book further states that his body was laid in rest in the oldest church of Manapad which has been now completely buried in the sand.
Constantine compiled the first Tamil lexicon - a Tamil-Latin dictionary. He also compiled the comprehensive Chaturakarati, a quadruple lexicon containing words, synonyms, and categories of words and rhymes. He translated and explained in Latin the "Thirukkural", an epic poem of Thiruvalluvar. This Latin work was an eye opener for European intellectuals, enabling them to discover truth and beauty in Tamil literature. He also translated into European languages several other important Tamil literary works such as Devaaram, Thiruppugazh, Nannool and Aaththichoodi. Besides composing literary Tamil Grammar work, he also wrote a grammar for the common use of Tamil, which at times led to him being referred to as the 'Father of Tamil Prose'. Earlier Tamil scripts were written without the tittle for consonants, and the symbol ர was used to indicate long vowels. It was Veeramamunivar who introduced the system of dotting the Tamil consonants and writing the long vowels as ஆ instead of அர, கா instead of கர, etc. His biggest poetical work is the Thembavani, 3615 stanzas long on salvation history and the life of Saint Joseph. He also wrote a prabandham called Kaavalur Kalambagam, a grammatical treatise called Thonnool, a guide book for catechists with the title Vedhiyar Ozukkam, and Paramarthaguruvin Kadhai, a satirical piece on a naive religious teacher and his equally obtuse disciples. His prose works include polemical writings against the Lutheran missionaries and didactic religious books for the instruction of Catholics.
