The four are all members of the Leophairatana family: Prateep, Prayad, Pramuan and Prachai.

The bourse also suspended trading of TPI Polene's (TPIPL) stock after it failed to make such a clarification in the first trading session.

Prachai is now TPIPL's chief executive officer, while Prayad, Pramuan and Prateep are presidents of different parts of the company's operations. All four are TPIPL executive directors.

Separately, Bangkok Union Insurance Plc, another listed company of which two executives and directors - Prateep and Malinee Leophairatana - were deemed unqualified for their posts, stated that there was no effect on its operation.

Prateep is on Bangkok Union Insurance's board, while Malinee is managing director and director.

Prachai, Prateep, Malinee, Prayad and Pramuan were all subject to lawsuits by the Department of Special Investigation on allegations that they had entered into a lease agreement to rent office space in TPI Tower for the benefit of particular persons while causing damage to Thai Petrochemical Industry Plc (TPI). "The SEC has already removed the mentioned persons from the SEC's executive database, which makes them unqualified as the management of TPI Polene and Bangkok Union Insurance," the stock exchange said in a statement yesterday.

Bangkok Union Insurance's second-quarter net profit fell from Bt5.81 million in the same period last year to Bt1.46 million, while TPIPL announced a unreviewed third-quarter net profit of Bt734.43 million, down from Bt772.56 million in the same period last year.

Meanwhile, TPI said that although Prateep, Pramual and Malinee are company directors, they had not participated in any management functions and there was no effect on the company.

Since a consortium led by PTT Plc acquired a controlling stake in TPI - another company set up by Leophairatana family - the company has restructured its management structure.

TPI will soon change the company's name to IRPC.