where he is slated to be reunited with his second cousin Ana Rosa Sivori, who came to the Southeast Asian country as a missionary 50 years ago.
Sister Sivori, 77, told Efe news on Friday that the Pope had suggested her name as his translator for his Thailand visit.
"It was a pleasant surprise for me and it is an honour," she said from the chapel of Salesian Sisters Convent here.
Sister Sivori, who learned the language "to reach the most disadvantaged population", will translate the Pope's sermons he would deliver in the country.
The two grew up together in Argentina and their grandfathers were brothers.
"As a child, Jorge (the Pope's given name) was very studious and loved soccer. Our family was very close, and in Argentina, we would always meet during family gatherings," said Sister Sivori.
She said Catholicism was in "good health" in Thailand despite a small community of followers of less than 400,000 or 0.58 per cent of the 60 million population.
Pope Francis will be on a three-day pilgrimage for peace and to promote inter-religious dialog.
The visit also coincides with the 350th anniversary of the Vatican's mission to Siam, Thailand's former name. The "Mission de Siam" was announced by Pope Clement IX in 1669.
The pontiff will meet Thailand's King Maha Vajiralongkorn, Prime Minister Prayut Chan-o-cha and the head of Buddhist monk Sangha, before he heads to Japan on November 23 to continue his Asian tour.
The pontiff's meeting with the Buddhist leader will be the most complicated for Sister Sivori as according to Buddhism, a woman cannot touch or sit next to a monk. She will, therefore, have to sit behind Pope Francis during the meeting.
"The Vatican does not understand it, but these things are ingrained in them and we have to adapt," she added.
Buddhist leaders have also imposed a series of restrictions on the use of a few religious terms in Thai which are related to Buddhism, a religion practiced by 95 per cent of the country's population.
Sister Sivori came to Thailand in 1966 as a missionary, a year after entering the religious life, and is currently one of the trustees of five Catholic schools for girls across Thailand.
The cousins last met in Rome in 2015.
( With inputs from IANS )