The Election Commission (EC) may be asked to rule on whether the involvement of the Progressive Movement's core figures in the Move Forward Party (MFP)'s campaign constitutes a violation of election campaign rules.
The secretary-general of the Association for the Protection of the Constitution, Srisuwan Janya, said he was considering petitioning the EC to investigate.
He was referring to Thanathorn Juangroongruangkit, Piyabutr Saengkanokkul and Pannikar Wanich who are the chairman, secretary-general and an executive of the movement, respectively.
As the movement's core figures could be considered "outsiders" under the organic law on parties and other related laws, their involvement in the MFP's campaign might constitute unlawful interference in a party's affairs and lead to further action, he said.
If the EC confirms that the movement's core figures are indeed outsiders, he said he would lodge a petition against the MFP with the Constitutional Court, which could result in the party's dissolution.
Mr Srisuwan on Thursday challenged the trio to prove the legality of their involvement in the MFP's election campaign.
Previously, Mr Srisuwan petitioned the EC to look into whether Trairong Suwannakhiri, chief adviser of the United Thai Nation Party, violated the election law over his remarks about the monarchy during a campaign last Saturday.