The Pheu Thai Party has urged the military to adhere to democratic principles after army chief Prayuth Chan-ocha refused to rule out launching a coup.
Gen Prayuth said on Friday that a coup "could happen", but would depend on the situation.
Pheu Thai deputy spokesman Anusorn Iamsa-ard said yesterday that although there has been no putsch attempt, there is no guarantee that a coup would not happen.
Mr Anusorn said he supports the army as it adheres to democracy, a principle to which the military has always been committed. The army is a key organisation which could bring peace to the country, he added.
The spokesman claimed there is an attempt under way to usher in a coup by independent bodies which are allied to the network that toppled the Thaksin Shinawatra government in 2006.
Meanwhile, the red-shirt United Front for Democracy against Dictatorship (UDD) has vowed to mobilise its own demonstrators if a coup takes place.
"Thai people have shut the door on coups and will not allow another one to happen," caretaker Deputy Commerce Minister and red-shirt leader Nattawut Saikuar said.
"Once a putsch happens, there will be a movement from people nationwide to show their opposition to the coup."
Mr Nattawut warned Gen Prayuth that he could encounter protests from both sides if the army staged a coup and urged the army chief to adhere to the rule of law.
UDD core leader Jatuporn Prompan said if the army staged a coup it would mean it had been colluding with anti-government protest leader Suthep Thaugsuban from the beginning.
"If a coup takes place, we have to fight and that is the only thing to do," Mr Jatuporn said.