Former actress Meghan, 36, wore £1,350 yellow gold and diamond stud earrings by Birks, a black belt and black stilettos as she rode in the Queen's carriage procession.
During Thomas' television interview on Monday, he also said he approved of Prince Charles, who ended up walking Meghan down the aisle at her wedding after Thomas was not able to due to health reasons.
The Duchess of Cornwall, Princess Anne, Princess Beatrice and Princess Eugenie were photographed not wearing theirs.
But Meghan is diving in heard-first, keen to experience a day at the races with her new extended family.
Meghan Markle and new husband Prince Harry stepped out at Royal Ascot for the Duchess' first time at the races.More news: Meghan Markle, Prince Harry wedding: Thomas Markle breaks silence
When asked if he thought Prince Harry was a "Trump supporter", Markle said: "I would hope not now but at the time he might have been".
While Markle's look was polished, the standout feature of her outfit was her black and white Philip Treacy hat.
It was a family affair on Tuesday as the royals came together for the annual Royal Ascot.
Over the weekend gone by, Meghan donned a floral printed wrap dress when she attended Harry's cousin's marriage.
Like her wedding gown, it was designed by Clare Waight Keller for Givenchy, and we don't think it's too much of a reach to say they share some common elements. The royal couple laughed as they congratulated Frankie, with Meghan giggling as Harry jokingly waggled his finger at the winning horseman after his show of affection.
The longtime royal servant called out the famous family for leaving Thomas Markle to fend for himself after he was thrust into the spotlight.