"Today was the deadline to name joint venture partners," AOT President, Nitinai Sirismatthakarn, told Reuters adding that joint ventures required a Thai lead firm.

The announcement comes ahead of bidding date on May 22.

The duty-free business is a major beneficiary of a tourism boom in Thailand, where arrivals exceeded 38 million people in 2018.

Bidders include hotelier Minor International Pcl and King Power Duty Free, Nithnai wrote in a Facebook post.

King Power Group, owner of the English Premier League's Leicester City Football Club, currently holds the licence for duty-free retail in Suvarnabhumi, the country's main international airport.

The existing duty-free licence is set to expire in 2020.

Other groups include a venture between a unit of Thailand's largest retailer, Central Group, with DFS Ventures Singapore, and another between Korea's Hotel Lotte with Bangkok Airways Pcl.

The third group includes Royal Orchid Hotel Thailand Pcl, Empire Asia Group, and a unit of travel retailer World Duty Free Group, WDFG UK.

AOT booked 16.7 billion baht ($526.2 million) from concession revenue in its last fiscal year, 13.3 percent more than a year earlier.

Concession winners will be announced on May 31 and then put to the AOT board for approval, Nitinai said.

The concession will begin on Sept. 28, 2020 and will expire on March 31, 2031.

(Reporting by Chayut Setboonsarng)