The 29-year-old glamour model, who allegedly bedded Man U ace Ryan Giggs, was among several stars to attend the launch of LoveLite - a non-invasive liposuction treatment - in London. Following a recent holiday in Italy, Thomas showed off her tan in a dark blue zip dress, pink blazer and nude and yellow high heels, the Daily Mail reported.
Although few would deny the Welsh model's figure looks amazing, she has been open about her battle to stay in shape.
She's currently the face of Slimsticks, which helps her fight off hunger.
"I never count calories. I've tried every diet but they don't work," she told the Daily Star recently.
"As soon as you come off it the weight piles back on. My approach now is to eat little but often.
"I go to the gym four or five times a week and combine that with doing Bikram yoga. I think all girls have issues about their weight. I don't think I'm the only person out there," she said.
Imogen's night out came after she was forced to cancel a club appearance last week after falling ill.
She was scheduled to appear at Tiger Tiger in Cardiff on Friday night.
Also at the party was 'I'm A Celebrity... Get Me Out Of Here!' star Jessica-Jane Clement, who covered up her pin-up figure in long skirt and blouse.
She arrived on the arm of her hairdresser fiance Lee Stafford.