Privy Council president Prem Tinsulanonda has lambasted populist policies, saying they weaken the country and the people.
Gen Prem said Wednesday Thailand was once a regional leader, but the many problems plaguing the country had stalled development.
Among the problems were populist policies that discouraged people from helping themselves, he said.
The Privy Council president was delivering a keynote address at the 60th anniversary of the Graduate School of Public Administration at the National Institute of Development Administration.
Corruption was the worst problem. It brought shame on the country and Thais must join hands to fight it, he said.
Some people divided corruption into several forms, such as conflicts of interest and abuse of power. But no matter what graft was called, corrupt people were cheating the country, he said.
Social values were also changing for the worse as some people, including youngsters, thought corruption was acceptable as long as they gained something from it.
He said he has made several calls for Thais to stop giving a wai to corrupt individuals. People must not even associate with cheats, Gen Prem said.
Meanwhile, former energy minister Pichai Naripthaphan has expressed concern over the economic development plan being put into practice by Deputy Prime Minister Somkid Jatusripitak, the new head of the government's economic team.
He said it will not solve the root causes of the country's economic problems.
Mr Pichai said he disagreed with Mr Somkid's contention that the country should rely less on exports which have dropped sharply over the past several months.
He said Mr Somkid should focus more on luring foreign investors who fear trade sanctions by the US and EU countries as Thailand remains under a military government.
Exports, domestic income and purchasing power must be driven up simultaneously if the government is to develop the country, he added.
The former energy minister also thought Mr Somkid had erred by suggesting that GDP should not be used as an indicator of the country's economy growth.
Mr Pichai said Mr Somkid predicted the country's GDP will grow by only 2% to 3% a year over the next five years despite the fact that based on the country's economic potential it could reach up to 5% or 6%.