The retired lighting director would "love" to speak to the monarch as he imagines the king also questions why he has so little contact with the Duke and Duchess of Sussex - who relocated to California after stepping down from royal duties four years ago - or their children Prince Archie, five, and two-year-old Princess Lilibet, and insisted neither of them "deserve" to be treated "so badly" by the couple.
Thomas - who has had no contact with his daughter Meghan since before she married Prince Harry in 2018 - told MailOnline's Mail+: "I would love to speak to him because I am sure he has as many unanswered questions as I do. Neither of us deserves the treatment we've received.
"He is going through cancer treatment and I'm not in the best of health. I'm not afraid of dying. It is what it is.
"I have so many questions I'd like to ask Meghan and Harry. The main one being, why have they treated not only me but the royal family and the King so badly."
Thomas was particularly saddened when he saw photos from last weekend's Trooping The Colour celebrations because Archie and Lilibet are "being denied the right" to get to know the children of Harry's brother Prince William, Prince George, 10, Princess Charlotte, nine, and six-year-old Prince Louis.
He said: "It struck me as very sad that Meghan and Harry's kids are being denied the right to know their cousins, who look like fantastic children.
"The relationship between cousins is a special one. There's a unique bond.
"I feel sad that Lilibet and Archie don't have the chance to get to know their cousins and take part in things like Trooping The Colour, which is their birthright.
"They are getting to the age where they will start asking questions, as all kids do.
"At some stage it's inevitable that they will ask their parents why they have cut them off from both sides of the family?
"They have two grandpas who want to see them, one of whom is the King of England. I never in my 80 years thought I'd be in the same boat as the King.
"The decisions Meghan and Harry have made will affect their kids for the rest of their lives. I find myself wondering how Archie and Lilibet will feel in a few years time when they realise all the things they have missed out on."
Thomas turns 80 next month and while he'll spend the day with son Thomas Jr. and speak to his eldest daughter Samantha on the phone, he isn't expecting to hear from his estranged daughter or her family.
He said: "I don't expect to hear from Meghan and Harry. I wish we could have worked this situation out. I was always ready and willing to do that."