He is also a self-published author and poet, and the staff at Bishopscourt love to read several of his poems to residents as part of Christmas celebrations each year.
Mr Thomas will celebrate his milestone today — no doubt with more poetry — alongside his wife, Audrey, at an extended family gathering.
Asked if there was a special drink he would like to celebrate with, he said: "No, I'm not a drinker. Just a cup of tea and a little bit of cake will do."
While he had no idea how he had managed to make it to 100, he suspected his healthy diet and the love of his wife may have had something to do with it.
"She keeps me young."
One thing is for certain — there are very few 25-year-olds in the world who can say they have a legitimate birthday card from the Queen.