Prime Minister Prayut Chan-o-cha has poured cold water on ousted premier Thaksin Shinawatra's proposal to amend the charter to prevent senators becoming "political tools" of the regime.
The deposed premier threw his support behind a rewrite of the section that allows senators to vote for a prime minister next year but his comments were met with brickbats from Gen Prayut.
"How can we simply ignore it [the charter section]?" Gen Prayut said to reporters after a mobile cabinet meeting in Nong Khai on Thursday.
Gen Prayut said he had no idea how his government might be able to make changes to the charter, which has not been fully implemented.
"I don't know what to do if they [critics] find the charter useless," he said.
The highest law, the 20th Thai constitution promulgated in April last year, has suffered many hurdles and setbacks.
The charter, dubbed by some as the anti-cheating version, was drafted by a Meechai Ruchupan-led committee, which succeeded the Borwornsak Uwanno panel after its draft failed to get the green light.
Though the constitution was later approved in the Aug 7 referendum in 2016, parts of its content have become bones of contention.
Branding the charter "shameful", sharp-tongued politician Chalerm Ubumrung, who oversees the Pheu Thai Party's election campaign, said on Wednesday he disagreed with Section 272, which enables the Senate to join the Lower House in voting for a prime minister.
Like Thaksin, Mr Chalerm wants this section to be deleted.
The Senate of 250 members will be hand-picked by the National Council for Peace and Order (NCPO). This has caused concern among many politicians and democracy advocates who fear senators will be political tools of the NCPO to secure the return of Gen Prayut as prime minister after the general election in February.
Though 50 of the senators will be selected from professional and social groups, it is the military regime which will have the final say on their approval.
The NCPO was also granted the right to choose 194 senators while six others are reserved for the three armed forces leaders, the supreme commander, the defence permanent secretary and the national police chief.
The constitution, written during the tenure of the military-engineered government, appears to be among issues targeted by the anti-coup camp after the NCPO decided to lift its ban on political activities on Tuesday.
Deputy Prime Minister Prawit Wongsuwon on Thursday said there no serious concerns about this group, except "people stirring conflicts with their words".
The latest Thaksin remarks will have no effect, Gen Prawit said.
Former anti-Thaksin protest leader and Action Coalition of Thailand Party founder Suthep Thaugsuban vowed on Thursday his party will protect the current version of charter against any attempts to amend it.
The constitution received 16.8 million votes in its favour the referendum, so everyone must respect the people's decision, he said.
