The 241-room property is located in the heart of Bangkok, close to the Siam Paragon Mall and the Royal Bangkok Sports Club.
It will offer panoramic city views from the 21st to 32nd floor, five restaurants and bars, a spa and banqueting facilities
The Sala Daeng BTS and Silom MRT stations are easily accessible from the hotel.
IHG currently operates nine hotels in Thailand.
Pan Pacific, which has run the site since 1995, was unavailable to comment on why the contract, which was up for renewal this year, will be pulled.