About 10 million people in the country have mental health problems and almost 11% of them are at risk of committing suicide, according to the National Economic and Social Development Council (NESDC).
Meanwhile, almost 16% of the population is regularly stressed out, it said.
Danucha Pichayanan, secretary-general of NESDC, said on Monday, upon the release of the agency's first quarter report on Thai society, that mental health has become a critical issue.
The Department of Mental Health said the number of psychiatric patients grew continuously from 1.3 million in 2015 to 2.9 million in 2023.
"Despite Thailand officially having 2.9 million patients who received medical treatment [last year], the actual number of those with mental health issues may reach as many as 10 million, as many people don't seek treatment," Mr Danucha said.
"This indicates we have a higher proportion of these patients than the global average and suggests there are a significant number of untreated cases."
A large chunk of the population is also at risk of developing mental health problems.
Between Oct 1, 2023, and April 22, 2024, the department found that the percentage of people with mental health problems who experience high stress levels stood at 15.48%, the risk of depression was 17.20%, and the risk of suicide was 10.63%.
These figures have worsened compared to previous years, Mr Danucha said, adding that mental health issues greatly impact the economy. The World Health Organization found that depression and anxiety contribute to the loss of about 12 billion workdays globally, resulting in an economic loss of over US$1 trillion.
Nearly one in five people with mental health issues are unable to care for themselves, requiring family care and leading to significant human resource losses, he said. Moreover, less than a quarter of high-risk psychiatric patients receive proper monitoring and care.
The NESDC also found that increased economic and social pressures have led to higher rates of depression and anxiety. In fiscal 2023, anxiety and depression were the top two mental health issues, surpassing the number of patients suffering from methamphetamine abuse and the abuse of other substances combined.
The suicide rate is nearly as high as it was during the 1997 Tom Yam Kung crisis, Mr Danucha said.
"In fiscal 2023, the suicide rate was 7.94 per 100,000 people, close to the rate during the Tom Yum Kung crisis at 8.59 per 100,000 people," he said, adding that environmental issues also impact mental health.
A study in the UK found air pollution increased depression in young people by 20%.
Mahidol University found that seven in 10 people in Bangkok experience burnout at work.