Palang Pracharath Party (PPRP) member Ruangkrai Leekitwattana has asked for a fresh Election Commission probe that could provide grounds for dissolving the rival Pheu Thai Party.
He has formally sought a commission investigation into Pheu Thai's recent appointment of Dr Surapong Suebwonglee as the party director.
Mr Ruangkrai, who defected to the ruling PPRP from Pheu Thai, insisted Dr Surapong was not qualified to serve as a main opposition party member, let alone its director, because of prohibitions under Section 98 of the constitution.
The section bars anyone released from prison less than 10 years previously from being a member of a political party. This ban is also reflected in Pheu Thai's own membership rules, Mr Ruangkrai claimed. Dr Surapong was released from prison in July 2017 after serving 10 months of a one-year term for malfeasance.
He authorised changes to a concession while information and communication technology (ICT) minister to allow Shin Corp to reduce its minimum shareholding in its satellite affiliate Shin Satellite, now renamed Thaicom, from at least 51% to 40% in 2004.
The court said he violated Section 157 of the Criminal Code which prohibits officials taking actions that cause damage to the state.
It said his actions were against the constitution and telecom law. They put the telecom business at risk from foreign dominance, the court said, adding Dr Surapong failed to seek cabinet approval for the concession change.
The Supreme Court's Criminal Division for Political Office-Holders convicted him on Aug 25, 2016, and handed him the one-year jail term. He was later freed early for good behaviour.
Mr Ruangkrai said Dr Surapong's conviction also stemmed from the abuse of his ministerial post, which was also grounds for barring him from political party membership.
Now that Pheu Thai has named Dr Surapong its director, it may have broken the law by having someone not qualified to be a member or have an important position in the party.
This may be construed as letting a person who is technically a non-member interfere in the party's affairs, which could provide a reason for disbanding the party, according to Mr Ruangkrai.
He also noted most parties have cited Section 98 in their respective regulations pertaining to membership.
Pheu Thai leader, Cholnan Srikaew, insisted the party's legal team has carefully examined the law and was confident Dr Surapong's appointment was above board.
He also said the party might take legal action against Mr Ruangkrai if he had the intention of damaging Pheu Thai's reputation.