Coca-Cola external affairs director Katie Meech, confirmed that 'part of that realignment naturally included a clause preventing creative services for competitor accounts'.
Sources close to Pepsi said that the forced move was a blow, after 18 years of working with Ogilvy PR in Bangkok.
They confirmed that the soft-drinks giant was actively looking for a new consultancy, although company officials were unavailable for comment.
Pepsi's task will be made more difficult by the fact that there are only a handful of PR consultancies of significant size and capability in Thailand.
A number of these - including Hill & Knowlton, Weber Shandwick and Aziam Burson-Marsteller - already work with various Coke brands.
Meanwhile, Ogilvy PR has not yet been appointed to work on the Fanta or Sprite brands alongside its advertising arm, but this is expected to happen soon.
Meech said that Coca-Cola had 'a roster of PR firms that we work with on a variety of brands and activities.
'It would be premature for us to comment on whether we would also work with Ogilvy PR in that roster until we receive confirmation that they no longer provide creative to competitor accounts,' she added.
Sources said that Ogilvy PR ceased providing its services for Pepsi on 15 July.
'We play by the rules and have already set up a new team (to work on Fanta and Sprite). We are awaiting a signal from Coke,' said Ogilvy managing director Chutharat Thanapaisarnkit.