The labour union of Thai Airways International (THAI) has accused company president Charamporn Jotikasthira of failing to generate revenue for the airline, and asked the prime minister to examine his performance.
Union president Damrong Waiyakanee and about 80 employees submitted a complaint to Prime Minister Prayut Chan-o-cha at the Government House public complaints centre on Wednesday morning.
They asked for an investigation of the national carrier's operations under Mr Charamporn.
The labour union accused him of inefficiency and of miscalculating the costs and depreciation of aircraft, alleging a hidden intention.
The union's complaint said the loss declared for 2014-2015 was not from actual operations. The main reason was the method of calculation of the value of the assets. The complaint alleged irregularity in the financial statement regarding the early retirement of aircraft that were still usable, in order to gain support for buying new aircraft.
Mr Damrong said the company had outlined investment plans that aimed to cater only for upmarket customers.
The company had also bungled its plan to save costs by staff cuts which affected the quality of service and safety. The plan put a burden on the company to pay more overtime.
He said the airline's executives did not recognise the value of operating employees and ignored problems raised by employees.