Daya first attended Southland Balika Vidyalaya, later joining St. Aloysius College, where he remained until after his G.C.E A/L examinations.
In 1970 he was transferred to Galle, and in 1983, he received a diploma in programming and systems design and was appointed as an Analyst Programmer at the Head Office of the Cement Corporation.
In his youth Daya Dissanayake contributed to the school magazine, and wrote articles for the Sinhala paper, Ada, popular at the time for fostering radical views.
While in school he was more popular as a photographer than a writer; other than winning an award in a competition held by the British Council, Colombo when he was in his twenties, his creative activities in his youth were confined to typing numerous short stories on a battered typewriter – stories which remain unpublished - and are largely lost.
His writing often features the subjects of non-violence, history, archeology, Buddhism and how people perceive and adopt religion in their lives.
His first novel was Kat bitha (1998) in which he narrates the story of Sigiriya through the musings of a young monk who visits the site in the 11th century.
Miracle Under the Kumbuk Tree (2012) won the Sri Lankan National Award for the Best English Novel.
Dissanayake's presentation of them, as of monks, evangelists and money makers is admirably unvarnished and knowledgeable," stated Regi Siriwardena, upon examination of Miracle Under the Kumbuk Tree.
He has also published a collection of poems titled Inequality, which reviewers from the Sunday Observer noted for its experimental use of language.
[7] Prof. Sunanda Mahendra wrote a glowing review for the Daily News, stating that "Daya is, to all intents, a reformer of sorts.
[4] He is vocal against what he describes as "the commodification of art" and has called for writers to place their works in the public domain, pointing out that with freedom of publication, writers "would write freely, for their own pleasure and satisfaction, and readers could read freely, of their own choice, without any control, or monitoring or censorship".