Thomas' fellow Team Sky riders Peter Kennaugh, Ian Stannard and Ben Swift have also withdrawn from the Games which start in Delhi, India in nine days time.
Welshman Thomas, who finished third in the mens scratch race at the British track championships in Manchester yesterday, has cited the risk of contracting mosquito-borne dengue fever and told BBC Wales: "It's a massive disappoint first and foremost but the hygiene and the risk of getting ill, it was a massive risk.
"I don't have a spleen any more and that fights infection, so that made it an even greater risk for me [to travel to India]. It's a massive disappointment, I only get to ride for Wales once every four years, but that's the decision I had to make."
Picture copyright of Covsupport News Service. Credit CSN/KM