In 1901, the Christians belonging to Chanthaburi numbered 2,500; in 1904, helped by his vicars, a French missionary, Father Augustin Peyrical began the construction of a new church.

Despite the material difficulties in maintaining the schools, the number of Christians continued to increase and in 1928, Father proceeded to bless a new church and a cemetery in Rayong.

[6] On December 23, 1945, Pope Pius XII erected the apostolic vicariate of Chanthaburi and therefore the church of the Immaculate Conception became a cathedral with a canonical chapter.

[7] Since 1965, it serves as the Latin rite seat of the Diocese of Chanthaburi (Dioecesis Chanthaburiensis, สังฆมณฑล จันทบุรี) created with the Bull Qui in fastigio of Pope Paul VI.

The shape of the Cathedral with a central nave, two side alleys, a narthex, and twin spires is an exemplary form of neo-Gothic expression.

Three other stained glasses in an oculus represending the blessed martyrs as Theophane Venard, Auguste Chapdelaine of the Paris Foreign Missions Society are a legacy of the French builders of this sanctuary.