The journalist-turned-novelist died at his home near Salisbury, Wiltshire, on Tuesday after a lengthy illness.
His widow Diana said: "He had a wonderful life and he travelled the world. All he ever wanted to do was write and that is what he did. He died at home with his family around him."
Thomas, who was born in Newport, Wales, grew up in a Barnardo's home and started work as a reporter on a weekly paper before moving to the London Evening News.
But it was his time as a national serviceman in Malaya that inspired his most famous work, a comic tale of British soldiers based in the Far East that became both a bestseller and a hit film.
Thomas went on to write scores of novels, non-fiction and travel books. He was awarded an OBE for services to literature in 2004.