Former prime minister Yingluck Shinawatra on Monday accepted the outcome of the referendum in favour of the new charter but said only limited criticism had been allowed and she regretted having a non-democratic constitution.
On her Facebook post, Ms Yingluck said she recognised the decision of people, but she would like to voice her opinions.
She was not surprised by the referendum outcome because critics had no freedom to comment on the contents of the draft charter. The atmosphere was unlike other referendums worldwide, she said.
She was happy to do a citizen's democratic duty by exercising her vote, even though hers was among the minority, she said.
However, she said she felt sorry that the country was stepping backwards to use a constitution that appeared to be democratic but was not truly so.