The posts were put up almost simultaneously on their accounts.
As of 9am, at least four Pheu Thai politicians had posted their pictures and messages opposing the draft.
The campaign raises a question as to whether it breaches the referendum law and other related laws, as the junta is attempting to ban activities that might affect the outcome of the August 7 referendum on the charter draft.
The referendum law restricts campaigns and propagation of the referendum and its subject, with violators facing up to 10 years of jail.
However, a Pheu Thai source said they were exercising their personal rights to voice opposition to the charter draft.
Some of Pheu Thai politicians campaigning against the draft via Facebook include the following:
"(The draft) is undemocratic and not in line with international norms. I can't accept it because the next generation will be in trouble for so long. So, I decide not to accept this draft."
Kittiratt Na-Ranong, former Deputy Prime Minister:
"I can’t vote for the draft, which is undemocratic. It will create more trouble for the country and the quality of life of the next generation.”
"For Democracy, people are the key. A constitution that does not respect and believe in the people’s faith violates international democracy principles. I can't accept it."
"I can’t accept a constitution that looks down on people's decision, establishes organisations to control the people's representatives and makes them unable to work independently."
Meanwhile, the Democrat Party has yet to make a decision on whether the party will vote “yes” or “no” on the draft, as party members are still divided, key member of Democrats Nipit Intrasombat told The Nation.
He added that the Pheu Thai online campaign was not in violation of any laws as it encompassed normal expressions of opinion. The Election Commission also confirmed people could voice their views on the draft..