The long-planned IPO follows a string of large Thai listings last year, with Central Retail Corporation Pcl and SCG Packaging Pcl each raising over $1 billion.

The Stock Exchange of Thailand plans to add 500 billion baht to its market capitalisation in 2021.

PTT set a preliminary price range for PTTOR shares between 16 baht and 18 baht, which would raise between 43.2 billion baht and 54 billion baht. ($1.44 billion to $1.80 billion)

PTTOR has placing agreements with 28 cornerstone investors, including SCB Asset Management, BBL Asset Management and Kasikorn Asset Management, it said in a separate filing on Thursday. Foreign cornerstone investors include Singapore sovereign wealth fund GIC, Asia Research & Capital Management, and JP Morgan.

The final price will be decided by Feb. 3, state-owned PTT said in a statement. PTT will hold 75% to 77.5% of shares after the IPO. PTTOR's main business is its 2,000 gas stations, but also 3,000 coffee shops under the Cafe Amazon brand as well as other restaurants. It booked profits of 5.8 billion baht in the first nine months last year, down from 8.9 billion baht in the same period a year earlier.

The company plans to use the IPO proceeds to expand its network of gas stations and invest in distribution centres for its oil business. The subscription period will run from Jan. 24 to Feb. 2 for retail investors and Feb 3-5 for institutional investors. Domestic financial advisers are Bualuang Securities , Finansa Securities, Kasikorn Securities, Phatra Securities, TISCO Securities.

Foreign initial purchasers include JP Morgan Securities, Morgan Stanley, and Merrill Lynch (Singapore), its filing said.

($1 = 30.0100 baht)

(Reporting by Chayut Setboonsarng; Editing by Ed Davies and David Goodman)