By Agence France-Presse
Thailand expects to welcome 41 million foreign visitors this year, the majority at its airports which rake in an estimated $1.9 billion a year in duty-free sales.
State-owned Airports of Thailand (AoT) awarded King Power the sole concession in 2006, which expires in September 2020.
King Power was founded by Vichai Srivaddhanaprabha, an astute tycoon who made billions from duty-free and invested in everything from hotels and property to Leicester City football club.
But the future of the company was thrown into uncertainty by his shock death last year, when his helicopter crashed outside the British club's home ground.
The new contract for duty-free sales, AoT said, would be managed by a single company with a proven track record of experience in the sector, creating fears of a prolonged monopoly.
But junta chief Prayut Chan-O-Cha said the government received complaints from interested parties "on the issue of monopolisation", a spokesman told reporters.
He assigned an urgent review of the bidding to find a "suitable process to be fair".
Thailand's Mall Group, shopping empire Central Group -- both backed by billionaires -- are eyeing entry into duty-free while South Korean giant Lotte is also in the hunt.
A lobby-group, the Thai Retailers Association, welcomed the review.
"I think it's a good sign," said Worawoot Ounjai, who is also an executive with Central Group.
He added that the current provisions for bidders were too stringent and left out less powerful competitors.
"Duty free operations are not that hard... and should be open to any business that will give you the most profits," he told AFP.
King Power, which rarely responds to media requests, could not immediately be reached for comment.
Last year, a Thai court rejected an attempt to sue King Power for hundreds of millions of dollars in unpaid revenue to the airport authority.
Fortunes are at stake in the duty-free sector as Thailand is poised to expand major airports and build new ones to accommodate surging tourist growth.
Thailand's former king bestowed Vichai the royal surname Srivaddhanaprabha meaning "auspicious and prosperous light".
Current King Maha Vajiralongkorn is expected to preside over Vichai's cremation next week.
Vichai handed his empire to his youngest son Aiyawatt. At his death the company was worth around $5.8 billion, according to Forbes.