AOT chairman Prasong Poontaneat said the National Council for Peace and Order was examining the project proposal to ensure its transparency.
The AOT was ready to begin the work as soon as the council gave it the green light. The expansion was essential to improve the capacity of the international airport to meet projected demand for services.
AOT plans to spend 62.5 billion baht on the second phase of Bangkok's Suvarnabhumi airport to increase its capacity to handle up to 65 million passengers per year, he said.
The first phase of the airport was designed to serve 45 million passengers annually, and actual traffic at the airport amounted to 48 million last year.
AOT earlier planned to start expansion construction next month and have it completed in three years.
The project includes a concourse with a useable area of 216,000 square metres and 28 adjacent aircraft parking bays, an additional aircraft parking area of 960,000 square metres, an underground passenger transport system and passenger terminal and airline office expansion.
AOT also plans to install an Advance Passenger Processing System (APPS) at a cost of 8.3 billion baht. The system will allow immigration, customs, airport and airline officials to obtain passengers' profiles from their countries of origin and they will be able to check if passengers are blacklisted or banned from leaving a country.
Authorities will share passenger information and ordinary passengers whose profiles are clean could pass immigration checks faster.
The number of air passengers visiting AOT's airports nationwide rose by 4.2% and the number of visiting flights increased by 13.2% year-on-year in this fiscal year. From last October to May AOT airports served 60.34 million passengers and 419,363 flights.