Before causing widespread alarm among Bangkok residents this year, PM2.5 fine dust particles plagued the skies in the North, Northeast and Central Plains for over a decade -- and it might be getting worse.
At some points on Tuesday, the air quality in Chiang Mai ranked the worst in the world. Many other provinces in the region have also suffered high levels of this microscopic particulate matter (PM), which is harmful to people's health.
PM2.5 refers to PM with a diameter of less than 2.5 micrometres. It can lodge in the lungs and enter blood vessels, leading to respiratory and cardiovascular disease.
With motor vehicle emissions a major source of PM2.5 in the capital, the smog in the regions is mainly caused by forest fires and outdoor burning activities on corn and sugarcane plantations.
This usually takes place from late January to April.
The authorities have focused on giving orders and enforcing laws to deter and punish farmers from open burning, as a swift response to the problem.
But this is not a sustainable approach.
It has in fact sparked resistance from farmers. Central and local state agencies should offer alternatives to outdoor burning instead.
Across the country, approximately 10 million rai of land is dedicated to sugarcane growing and 7 million to planting corn.
In several areas, sugarcane harvesting is done by setting fire to plants first to burn their leaves and making it easier to manually cut their stalks. It is time- and cost -effective for farm owners to do this.
Others opt to cut the crops manually without burning, which takes more time. Sugarcane-harvesting machines have also been used by those who can afford them. Each machine costs several million baht.
Meanwhile, corn growers light fires on their plantations after the harvest to clear the land for a new round of planting. This is also time-and cost-effective.
There are alternatives to these practices. State banks could provide low-interest loans for farmers to buy crop-cutting machines.
State agencies could promote the development of affordable technologies to help with cutting crops and clearing land for a new harvest.
For example, a portable biomass shredder with 60 blades, developed in 2016 by the Rotary Club of Lampang, has proved a success.
The club gave free shredders to a number of local farmers and taught them how to make organic fertiliser from the waste, which they can sell at markets.
Companies that purchase produce from farmers, especially big agricultural companies that benefit handsomely from the corn they buy and use as animal feed for their business, should also do their part in reducing the practice and the resultant air pollution.
They could start to provide incentives, such as better prices, for farms that eschew open burning.
The state should think about certifying products not sourced from this agricultural practice of burning to clear their land.
As this type of hazardous haze moves hundreds of kilometres across neighbouring countries, Thailand as the current Asean chair this year should lead the region in revisiting its commitment made in 2002 to combat the smog.
Tacking the air crisis will not be easy by any means.
The task requires integrated and innovative solutions that go beyond simply blaming farmers for open burning.