The Group of 40 Senators, an anti-government faction in the Senate, has called for greater clarity in the amnesty bills for political offenders.
The group is concerned that certain aspects of the bills could be misinterpreted and be used to grant an amnesty to holders of political positions.
The amnesty bills should apply only to civilians involved in political violence, the senators said, while any politicians who were involved, such as protest leaders, must be held accountable.
The call follows talks last week between the rival yellow- and red-shirt camps who have been behind most of the major political demonstrations in recent years.
The meeting was arranged on Thursday by deputy House speaker Charoen Chankomol to discuss an amnesty deal for convictions stemming from political protests since the Sept 19, 2006, coup.
The two sides informally agreed that participants in political gatherings should be spared punishment, while protest leaders found guilty of crimes must be brought to justice.
However, the Group of 40 Senators objects to the term "innocent people" in the amnesty bills, saying this was too broad and would need interpretation.
They worry this could be used to include politicians and protest leaders.
Furthermore, over 1,000 people detained in connection with the political violence had been released on bail using money from the Justice Ministry's Justice Fund, he said.
Only about 30 suspects who were facing serious criminal charges were still being held at the detention centre in the Lak Si area, Mr Somchai said.
"Should these suspects be included in the amnesty efforts as well?" he asked.
If the government really wanted to grant an amnesty to these suspects, it merely needed to instruct the police, the Department of Special Investigation and public prosecutors to not indict them, Mr Somchai said.
However, those who were involved in the murders of nine military officers and two police and the wounding of hundreds of people must not be absolved, he said, otherwise more political conflicts would arise.
Mr Charoen said separate amnesty bills should be drafted _ one for non-politicians and one for protest leaders.
He met Pheu Thai leader Charupong Ruangsuwan to discuss the amnesty bill matter yesterday. The two bills should be submitted to parliament at the same time, he said.
Mr Charupong said he would have to discuss the two-bill proposal at the party meeting and let the party executives decide if they would support it.