Thomas, who came out as gay in 2009, is thought to be the first UK sportsman to go public about living with the virus.
The Welsh star said the Duke of Sussex has ‘done so much to normalise HIV testing and fight the stigma across the globe’.
The ex-captain of the British and Irish Lions recently revealed he has HIV.
The former Wales rugby captain revealed he has been diagnosed with the virus.
The former Wales captain, who played for French team Toulouse for three years, was a victim of a homophobic assault in Cardiff last week.
The viewers' vote on the popular ITV entertainment show was cancelled after rugby star Gareth Thomas pulled out with illness.
Former Wales rugby captain Gareth Thomas has told Daybreak that Hollywood star Mickey Rourke will play him in a film about his life.
Watch the full interview on the Daybreak website.