Pruet signed the lease with American airline Southern Air while he oversaw the cargo department, without seeking approval from the board of directors, THAI president Piyasvasti Amranand said.
The contract, said to be struck at an extraordinarily high rice, was signed 14 days before Piyasvasti officially took the helm.
The disciplinary investigation has been completed, the president said after a board meeting yesterday.
Along with Pruet, the board also moved Charatpong Burutratanaphan, vice president for general administration, as another special adviser.
Teerapol Chotichannapibal, managing director of the catering department, was appointed acting executive vice president and replaces Pruet. Griangsak Sakruangngam, deputy vice president for the general administration department, was appointed acting vice president for general administration.
The board yesterday revealed that THAI's cabin factor, averaged 65.50 per cent in June, dropping 15.58 per cent from May even though tourism authorities insisted that the number of tourists to Thailand had recovered from the sharp fall in May following the political turmoil.
In the statement issued after the board meeting, THAI said the available seat per kilometre (ASK) in the second quarter was 2.62 per cent higher than the same period last year, while revenue passenger kilometre (RPK), a measure of the volume of revenue passengers carried, was 0.19 per cent higher. The cabin factor averaged 64.63 per cent, which was 2.36 per cent lower than the same period last year.
In June alone, ASK was 7.58 per cent higher than in June 2009, and 4.08 per cent lower than in May 2010, while RPK was 8.30 per cent higher than in June 2009, and 10.87 per cent higher than in May 2010. The cabin factor averaged 65.50 per cent, which was 0.67 per cent higher than in June 2009.
For the first half of July, RPK was 8.90 per cent higher than the same period in 2009. The cabin factor averaged 73.50 per cent, pointing to a return to normal of air traffic and air travel of passengers. THAI also said that it is witnessing excellent advance bookings.
The cargo business in June showed a 58.23percent increase on month. Load factor averaged 65.27 per cent, which was 26 per cent higher than the same period last year.
The board also approved German firm Recaro Aircraft Seating to suppy economyclass seats, replacing Kioto Industries, for six Airbus 380 8000 aircraft. Recaro Aircraft Seating met the technical requirements and their proposal offered the most benefit, the airline said.