Former prime minister Anand Panyarachun has called for a new constitution to be drawn up to ensure full democracy and people's fundamental rights.
He said there have been few positive changes in terms of people's rights, and the call for basic rights has not yet been answered in Thai society.
A new constitution should serve as a tool to transform the country into a just society with less inequality, Mr Anand said.
He was speaking to reporters at an event in Bangkok on Tuesday marking the 30th anniversary of the 1992 Black May tragedy in which dozens of street protesters were killed in a military crackdown.
Mr Anand said the priority is to overcome poverty because as long as people are still poor, their rights under the constitution will be meaningless.
Apart from political problems, the government should focus its attention on addressing problems affecting people's daily lives to ensure they have access to housing, medical care and basic necessities.
"I want to see the government pay more attention to these matters and take serious action, not just pay lip service," Mr Anand said.
He also emphasised the need for all involved in political conflicts to talk to foster reconciliation and mutual trust which will pave the way for peaceful co-existence.
"People can hold different opinions, but they must not be hostile towards each other," Mr Anand said.
He also said the Black May tragedy should serve as a lesson to avoid conflict and people should learn to forgive and forget.
"Refusing to forgive and forget will only fuel hatred in people's hearts. If we fail to learn from mistakes in history, it will be difficult for Thailand to find peace....We have to build mutual trust. Even if we are not friends, we will not make enemies. This will take a lot of time and effort," Mr Anand said.