Airlines are braced for two obstacles that could force them to increase surcharges to survive and maintain revenue.
Mr Sumeth says the market situation and competition will determine fares.
Transport Minister Arkhom Termpittayapaisith said the first speed bump is the new restriction on airfare ceilings. The Civil Aviation Authority of Thailand (CAAT) is finalising paperwork that is expected to be endorsed soon.
The new restriction will lower the maximum air ticket price from 13 baht per kilometre to 9.40 baht. But this initiative will not include routes of 300km or less such as Bangkok-Samui and Chiang Mai-Chiang Rai. The maximum price for short routes will remain unchanged at 17 baht per km.
"Every airline must follow this ceiling price rule," Mr Arkhom said. "However, they may increase other surcharges based on operating costs."
He said the continued rise in global oil prices forced airlines to increase their fuel surcharges, and Thai Airways International Plc (THAI) is among those airlines.
Sumeth Damrongchaitham, THAI's newly appointed president, said the increase in airfare will be based on the market situation and competition, but it must remain below the ceiling.
"We are selling tickets below the ceiling," Mr Sumeth said. "Before we adjust prices, we will consider many factors regarding this issue. We do not want to increase ticket prices and drive off customers. We must survive."
THAI already announced an increased fuel surcharge of 768-12,800 baht, starting from Sept 14. The additional surcharge is based on increases in the global oil price index.
As a result, fares on THAI's 58 international routes in 11 clusters will increase. Passengers on short distance routes such as Yangon, Ho Chi Minh City, Hanoi, Vientiane and Phnom Penh will be asked to pay an extra 768, 1,152 and 1,280 baht for economy, business and first-class tickets, respectively.
Most surcharges will be for the Bangkok-London route at 4,608, 9,280 and 12,800 baht for economy, business and first class, respectively.
An executive at low-cost carrier Nok Air said that if CAAT announces the new scheme in the near future, it will hurt airlines.
CAAT said any regulations must be announced 30 days ahead of implementation.
The Nok Air executive, who asked to remain anonymous, said the measure will hit low-cost carriers the hardest as they face the stiffest competition. Most sell below ceiling prices, except during peak periods.
"Some low-cost airlines put zero-baht campaigns on the market, but later they can earn revenue from other services such as food and drink, souvenirs, luggage and other items," the source said.
Full-service airlines are unlikely to be hit by the scheme, as they sell few tickets at the lowest possible prices.
An aviation expert said that if the new ceiling price is enforced, most low-cost airlines will have to cut fares.
But this will not be reflected in airlines' revenues, as they will increase other services. The net result will be that passengers will pay the same rates or higher than before the revision.
"Eventually, airlines need to survive and maintain their revenue and profit," the expert said.
Representatives of Thai AirAsia and THAI Smile said they would follow the new rules, while revising their business strategies to respond to competitors.
They said the government should set minimum prices instead of price ceilings, similar to public buses and ferries, so that customers can gauge whether to use airlines or other means of transport.
