She will be buried next to her late husband, although she has had another partner and child since the poet's death in 1953, and her marriage to Thomas was often punctuated by stormy rows and his extramarital affairs.
Caitlin Thomas's daughter, Aeronwy, said her mother had made the request to be buried next to her late husband, and the family would honour her wish, though they were surprised by it.
Her body will be returned to Wales and buried at Laugharne, Dyfed. It was there that Thomas wrote most of Under Milk Wood.
The pair married in 1936 after meeting in a pub. 'He didn't hesitate at all - he just seemed to know that this was it, or I was it, and I felt very good next to him, although he was not my dream of the romantic ideal,' she once said.
'I wouldn't have married him if he had not got the genius. He was too unattractive as a man.'
It was a notoriously stormy marriage, fuelled by alcohol and eventually riven by Dylan's affairs. She once memorably called their lives together 'raw, red bleeding meat'. They had three children - Llewelyn, Aeronwy and Colm - and lived at the Boat House in Laugharne.
After the poet's death from drink in 1953, his widow met a Sicilian, Giuseppe Fazio. He persuaded her to stop drinking. They had a son, Francesco, when she was 49.
After living in Italy for many years, she died in Catania on Sunday following a long illness.
In 1957 Caitlin Thomas published Leftover Life to Kill (1957), a frank account of her life with Dylan. She would not collaborate with her husband's biographers in the succeeding years
Obituary, page 12