Future Forward Party leader Thanathorn Juangroonruangkit can attend the opening ceremonies of Parliament and take an oath as an MP but cannot vote for the parliament president.
Mr Thanathorn became an MP so he could attend the opening of Parliament on Friday and be sworn in, Mr Wissanu said.
However, he would not be able to vote for the parliament president because the Constitutional Court ordered him to not perform an MP's duties, Mr Wissanu said.
The opening of Parliament was set at the Foreign Ministry's Vithes Samosorn Hall at 3pm on Friday.
After the official opening, the Senate would choose the Senate speaker and deputies at the auditorium of TOT Plc headquarters on Chaeng Watthana Road at 5pm. MPs were scheduled to meet there on Saturday to vote for the House speaker and deputies.
On Thursday the Constitutional Court decided to try a case in which Mr Thanathorn was accused of being unqualified to run for the March 24 for having shares in a media company. The court also decided to suspend his MP's duties until it delivers a ruling on the case.
The saga began after the Election Commission (EC) said that Mr Thanathorn still held shares in V-Luck Media Co when he registered as an MP candidate in early February.
Mr Thanathorn denied the charges and said that he and his wife transferred their shares to his mother on Jan 8, immediately after returning from Buri Ram province to Bangkok following a campaign rally.
The EC said that V-Luck Media Co is registered with the Commerce Ministry's Department of Business Development to run a newspaper/mass communications business.
The company's financial reports show its revenue comes from sales of magazines and advertisements, and so the company is a media business, the poll agency said.
A copy of the company's shareholder list — known as Bor Or Jor 5 — which the EC obtained from the Department of Business Development also shows Mr Thanathorn as a shareholder from 2015 to March 21 this year.
Since MP candidacy applications were held between Feb 4-8, if Mr Thanathorn was still a shareholder on March 21, then he was not qualified to apply as a candidate.
Mr Thanathorn's ownership of shares in a media company when he contested in the March 24 polls may constitute a breach of Section 98(3) of the constitution, which bars owners and/or shareholders of media and/or publishing firms from running as MPs.
Those found guilty could have their MP status revoked under Section 101(6) of the constitution.