The call from an opposition senator follows the deaths of two Thai soldiers in a coordinated resistance attack in the Shia holy city of Karbala on Saturday.
Two sergeant-majors in the army engineering corps were killed in a multiple car-bomb and mortar attack by Iraqi insurgents that also left seven Iraqis dead as well as four Bulgarian troops.
The six coalition soldiers were members of a 9000-strong Polish-led multinational division, and their deaths were the first losses in Iraq for Bulgaria and Thailand.
"We feel sorry that what we had warned the government about has now really happened," Kraisak Choonhavan, the parliamentary chairman of the foreign affairs committee, said in a live interview on Thai radio.
"We think we must pass again our concern to the government asking whether it is time to pull our troops out. It is time to review that decision," Kraisak said.
No withdrawal plans
On Sunday prime minister Thaksin Shinawatra said Thailand had no plans to withdraw its medical and engineering troops from Iraq despite the deaths of the two soldiers.
He told reporters Thailand's troops in Iraq would continue their humanitarian work while the military assessed the security situation.
"As of today, there is no change in our presence there as the morale of our troops remains high. Our second contingent is due to be there to replace the first batch that will complete its assignment in March," Thaksin said.
Thailand sent a 443-strong contingent of engineers, medical teams and a surveillance platoon to Iraq in September after Thaksin, who remained neutral during the US-led invasion, joined the American-led coalition.
The commitment was criticised by some 65 of 200 senators, including Kraisak, and the contingent was eventually halved from an original plan of 886 troops over budget concerns.
Kraisak said the occupation was not helping Iraq.
"I believe we are not ready to be part of the coalition force, and I think some senior military officials will think like me now. We are not ready for this war."