The haze that covers much of the northern region and poses health hazards to residents is a relatively new phenomenon. Less than a decade ago, forest fires were a concern, but never the kind of threat they are now.
Traditional views hold highland tribe people responsible for setting the forests on fire with their slash-and-burn farming practices. But these views can no longer stand because circumstances demand a different outlook.
The highlanders have practised slash-and-burn farming for millennia. While their practice does cause forest fires, it is not responsible for the severity of the air pollution gripping the region now. Something else is obviously at work.
Northern haze began to rear its ugly head in 2007.
BioThai Foundation director Witoon Lianchamroon said that same year the price of maize for animal feed jumped more than 20%.
During a discussion on haze pollution at Chulalongkorn University on Wednesday, Mr Witoon showed a graph that demonstrates the close relationship between the prices of maize and the number of forest fires or hot spots across the region.
When the price shot up to a peak of 9.35 baht in 2012, the number of hotspots jumped to more than 25,000.
When the phenomenon began to make news, most people had little idea about what caused it. Many still believed the hilltribe people were to blame.
Public awareness of the problem received a real boost after Nan province began to be hit by severe floods every year since 2010. Flooding in the province was nothing new, but its severity and frequency became suspect.
Not long after, photos of denuded mountains in the province were published and widely shared, bringing the shocking reality out into the open.
Large numbers of people expressed outrage and despaired that the Nan mountains they knew and loved had been covered with verdant forests not so long ago.
It transpired the mountain-top forests had been decimated to pave the way for maize plantations.
As this year's haze has developed into the worst since the crisis began, people are demanding action, not only from the government, but also from business operators who benefit from the crop, including CP Group and Betagro Group.
Both conglomerates are major food producers, but it is CP which receives all the unenviable attention.
As the country's largest consumer of maize and the world's largest producer of animal feed, CP cannot deny it has benefited tremendously from increased maize production.
It also cannot deny its role in the pollution crisis.
However, the company's response so far leaves much to be desired.
CP argues that most of the fires happened in forest areas and that only a small number of fires took place on farms.
The company also says it can only impose environmental conditions on farmers under its supplier contracts, which represent only a small portion of the total number of maize farmers.
But the figures it cited for forest fires are most likely flawed, taken from official statistics which critics say — and some officials confidentially agree — are unrealistic or out of date.
Statistics show that maize plantations cover over 3 million rai in the North alone.
Mr Witoon predicted that the figure would soon reach 3.5 million rai. Much of these areas used to be forests.
Most maize farmers sell their produce to CP which has an 80% share in the maize seed market. Obviously, they are not all contract suppliers with CP.
CP also acquires maize from farms in neighbouring countries, notably Myanmar and Laos. Myanmar, particularly, faces similar problems of severe forest loss and haze pollution which exacerbates the crisis in Thailand.
But CP and other food production companies alone are not to blame.
The expansion of maize plantations could not have happened without massive forest encroachment, as photos from Nan verify.
A question that immediately springs to mind is: How could forests on mountain upon mountain be cleared so completely without the knowledge and intervention of officials? The answer is: They couldn't. Not without implicit consent, and even support, from authorities.
Without doubt, many officials and politicians were responsible for this. I suspect many of the people involved are still working in this government.
Gen Prayut Chan-o-cha's government has shown it can be tough on public land and forest encroachers. The current haze crisis deserves its full attention.
There are two immediate tasks the prime minister can initiate.
He must stop any further forest encroachment, investigate who is responsible for the destruction of mountain-top forests in Nan province, and bring them to justice.
The mission is not impossible, what with all the power in Gen Prayut's hands — unless figures with more influence than he intervene to put a stop to his efforts.
Wasant Techawongtham is former News Editor, Bangkok Post.