A new political party has already been prepared for members of the Future Forward Party (FFP) to migrate to if the party is disbanded for undermining the monarchy, party secretary-general Piyabutr Saengkanokkul said.
The Constitutional Court will decide this Tuesday whether the party should be disbanded over the allegations.
The lawsuit was initiated by Natthaporn Toprayoon, a lawyer and former adviser to the chief ombudsman.
In the middle of last year, Mr Natthaporn filed a case with the court asking it to dissolve the FFP for violating Section 49 of the charter, which prohibits actions that undermine the monarchy.
In the lawsuit, Mr Natthaporn included party leader Thanathorn Juangroongruangkit, Mr Piyabutr and party executives for undermining the monarchy. He also cited the party's regulations and speeches and lectures delivered by senior party figures as pointing to the same trend.
However, if the court rules to disband the party, all its MPs, as well as its more than 60,000 party members will switch to a new party which shares the same ideals, Mr Piyabutr said.
He added that even if the party is dissolved and its executives banned from politics, he and party leader Thanathorn Juangroongruangkit will continue to engage in political debates nationwide so as to "render the party's disbandment ineffective".
Asked if he will lead people to take to the streets if the party is disbanded, he said freedom of expression is important to democracy.
"If politics in the formal system can respond to the people's needs, street protests will be limited accordingly," he said.
Meanwhile, in a Facebook post, activist Srisuwan Janya responded to Mr Piyabutr's warning of grim consequences if the FFP is disbanded.
On Friday, the FFP secretary-general said disbandment of the FFP would dash Thais' hopes and dreams of better politics, and this will also lead to "a clash of generations".
In response, Mr Srisuwan wrote on social media the disbandment of the party will be a boon for society and politics, shatter the political aspirations of FFP executives who will be banned from politics and allow rank-and-file members to assume a larger role.
"The dissolution will create unity among Thais including among different age groups because there will be no one to drive a wedge between the old and new generations," according to Mr Srisuwan's post.