Public Health Minister Somsak Thepsutin rejected a proposal from health experts calling on the ministry to review the co-payment system for the universal healthcare policy, also known as the 30-baht gold card scheme.
Mr Somsak said he did not wish to discuss the co-payment plan anymore.
"The ministry is doing its best to take care of people's health. No changes have been made," he said on Wednesday.
Mr Somsak was answering reporters' questions on whether the scheme could be due for review after a network of hospitals and medical staff recently came out to say it has been causing problems for state-owned hospitals. Many are now reportedly facing increased patient visits, staff shortages and financial deficits.
The network called on the ministry to reform the scheme in the interests of financial sustainability.
The populist policy, initiated by the now-dissolved Thai Rak Thai Party of former prime minister Thaksin Shinawatra over two decades ago, aims to provide equality in medical treatment for Thais, especially the poor.
It was first launched in 2002 with the requirement of a 30-baht co-payment per visit.
However, that was removed a few years later, allowing cardholders the right to access medical treatment free of charge.
Mr Somsak said he was confident the government could resolve the network's financial issues, potentially by drawing on the central budget.
"The amount of money missing from the co-payment system is just 2%, which is very small, and we can handle it. The scheme is being run well. Some people have criticised it despite the fact they lack the correct information," he said.
To subsidise the losses racked up so far from providing treatments, the National Health Security Office (NHSO) has requested an additional 7.1 billion baht.