Democrat Party chief adviser Chuan Leekpai has warned the new constitution must not push the country backwards.
He also stressed the importance of an election for the development of democracy.
Speaking at a seminar on the draft charter organised by the Constitutional Court, Mr Chuan said democracy has been adopted as the country's governing system and it must be allowed to develop further.
He said its progress has been stalled at times, but a retrograde step must be prevented.
Commenting on the draft charter recently completed by the Constitution Drafting Committee (CDC) led by Meechai Ruchupan, Mr Chuan said he did not think the Meechai version is an improvement on previous constitutions.
"This draft charter is not a step forward and no better than previous ones," Mr Chuan said.
He stressed the significance of an election for cultivating democracy.
"Don't run away from elections. If there are problems, fix them. But we should not move backwards because we've already come a long way," Mr Chuan said.
Mr Chuan said the constitution itself had not caused the country's problems, but the blame lies squarely on law enforcers and those in power who violated the constitution.
Mr Chuan noted the reason behind the coup on May 22, 2014 was partly that people responsible for safeguarding the law failed to carry out their duties properly.
"I wanted the National Council for Peace and Order (NCPO) to explain to the public why they seized power so the public knows the truth,'' Mr Chuan said.
''It was the failure to respect the constitution and the rule of law," he added.
He stressed the laws of the kingdom must be upheld and the country must adhere to parliamentary democracy with the King as the head of state.
While Mr Chuan commended the draft charter's rigorous measures to stamp out corruption, he noted a constitution is not intended specifically for anti-graft purposes.
The general principle of a constitution is to define the roles and tasks of organisations involved in governing the country, he said.
He also pointed out the merits and weaknesses of both elected MPs and coup-appointed ones.
While election candidates may buy votes to come to power, an appointed chamber such as the National Legislative Assembly (NLA) was also criticised as several of its members are soldiers with close ties to the military regime, Mr Chuan said.
Jade Donavanik, an adviser to the Meechai charter drafting panel, told the seminar he sympathised with the charter writers who were expected to meet high expectations from the public and other stakeholders.
Mr Jade, also a former member of the previous Borwornsak Uwanno charter drafting panel, admitted the panel could not work independently as the other four of the so-called five rivers of power -- the NCPO, the NLA, the cabinet and the National Reform Steering Assembly (NRSA) -- could influence how the draft charter was shaped.
Mr Meechai, who was present as a guest speaker at the seminar, said the draft charter aimed to combat corruption, address the lack of discipline among people and deal with lax law enforcement.
The draft charter is designed to tackle graft by preventing those with a history of corruption from running in elections.
Anti-graft mechanisms will also be put in place to monitor those in power.
Mr Meechai said education reform will be a way to address the lack of principles among people.
He said the state would fund free compulsory education starting from kindergarten to mid-secondary school.
Regarding charter measures to improve law enforcement, Mr Meechai stressed police reform must be completed within one year.
He said the police force is important as they oversee the first stage of judicial proceedings.
Chaisit Trachoetham, chairman of the State Audit Commission (SAC), said the draft charter attaches importance to financial discipline within the government as well as state audits.
The draft charter empowers the SAC, the Election Commission (EC) and the National Anti-Corruption Commission (NACC) to issue a joint resolution as "a risk warning" to halt any government project that could be damaging to the country. It would help alert both the public and politicians.
They can then forward their decision to the cabinet and parliament for further action.
This provision is a proposal from the SAC based on its experience with the Yingluck government and its flagship rice-pledging scheme which incurred huge losses for the state, Mr Chaisit said.
