In one ad, Ramsay takes a bite of some pork belly and says: "A little bit oily, right, but blend it with this beer and all of a sudden that oiliness goes, and you've got that fresh and crispness, it's delicious." The spot ends with Ramsay taking a swig of Cass and stating: "Bloody fresh."
One Twitter user stated: "Internet, I will provide 20,000 won ($18) for conclusive proof that Gordon Ramsay was a Cass drinker before he started endorsing it. Please retweet."
Ramsay spoke at a press conference in Seoul on Saturday to promote his involvement with the beer. "The authenticity of Korean food with the number one beer for me felt like a perfect match. It's by far the freshest, coolest… and also in these difficult times, with the economy in recession, it is a beer that can easily be bought and have some fun with. It's not pretentious," he said, according to the Korea Herald.
"(Cass is) something I drank before the call (for the endorsement) came in. When I have Korean food, I don't look for a wine list with the most expensive beer to go with it," he added.
Anheuser-Busch InBev, which owns Cass, says it is the number one beer brand in South Korea. It has a "crisp and refreshing taste," the brewer states on its website and suggests that it goes well with spicy food, Korean barbecue and fried chicken.
In a statement emailed to CNBC by AB InBev's global director of external communications Europe Peter Dercon, Ramsay said that beer preference is about personal taste. "Beer is something you drink as you like. I prefer beers that get along well with the taste of foods," he said, adding that light lager is a good match for strong-tasting Korean food.
The brewer bought South Korea's Oriental Breweries, parent company of Cass, for $5.8 billion in 2014.
This article has been updated to include comment from Gordon Ramsay.