Wikipedia has a pretty good intro into Pierre Martin Ngo Dinh Thuc. https://en.wikipedia.org/wiki/Ng%C3%B4_%C4%90%C3%ACnh_Th%E1%BB%A5c
However, there is much more to the story and the poison fruit produced through this man.
A schismatic group helped by Archbishop Thuc. They required their own Bishops to give the appearance of validity. https://en.wikipedia.org/wiki/Palmarian_Catholic_Church gives a basic history and shows how far off the rails this group has gone.
Following the illicit and cannonically illegal consecrations at El Palmar de Troya, Archbishop Thuc and any bishop or priest were excommunicated. Their "orders" were invalidated and nullified. http://www.vatican.va/roman_curia/congregations/cfaith/documents/rc_con_cfaith_doc_19760917_illegitimas-ordinationes_en.html
Archbishop Thuc recanted his heretical positions and renounced his error in having attempted ordination at El Palmar de Troya. Many of the men involved also recanted and returned to lay life. Thuc had the excommunication lifted and returned to his life in exile.
Archbishop Thuc was no forced to rely on the generosity of others for room and board. This did not sit well with the lifestyle to which he was accustomed. He became a "bishop for hire" as a means to support himself. As as sort of mercenary, he was selling his services to the highest bidder. Even some sedevacantist sources recognized the wide variety of people he attempted to "consecrate" to the episopate or "ordain" as priests. Of note were at least one satanist and several women. During this time he aligned himself with sedevacantist groups and consecrated bishops once again.
Following the consecration of Mexican and American sedevacantist bishops, the Vatican reinstated the excommunication decree of 1975. https://www.nytimes.com/1983/04/08/world/around-the-world-vietnamese-archbishop-excommunicated-again.html This document also renewed the invalidity and nullification of any orders conferred. This is important as the bulk of orders claimed by sedevacantist groups in North America stem from Thuc and are summarily invalid. http://www.vatican.va/roman_curia/congregations/cfaith/documents/rc_con_cfaith_doc_19830312_poenae-canonicae_en.html
Archbishop Thuc was nearing the end of his life when he was contracted to consecrate one French and two Mexican as bishops. The renewal of his excommunication must have hit him hard. His health and mental faculties were failing him. However, prior to his death, he once again reconciled with Rome (see text below) and recognized that he had acted in error when he raised unworthy men to the episcopate for a quick payday. As before, he urged these men to renounce their false orders and return to lay life. Sadly these men did not and the poison has spread throughout the Traditionalist movement.
Archbishop Thuc's renunciation of the illicit and illegal attempts at ordination/consecration was found in a Section from a Sedevacantist book. The pertinent text regarding the statement of Thuc to John Paul II and anyone who he ordained or consecrated:
"I, undersigned, Peter Martin Ngô Ðình Thuc, Titular Archbishop of Bulla Regia, and Archbishop Emeritus of Hue, wish to publicly retract all my previous errors concerning my illegitimately ordaining to the Episcopate, in 1981, several priests, namely Revs. M. L. Guérard des Lauriers, O. P., Moses Carmona, and Adolpho Zamora, as well as my denial of the Second Vatican Council, the new 'Ordo Missae', especially the dignity of His Holiness, Pope John Paul II, as actually legitimate successor of St. Peter, published in Munich in 1982.
I wish to sincerely ask you all to forgive me, praying for me, and redressing all scandal caused by such regrettable actions and declaration of mine.
I would also like to exhort the above mentioned priests who had illegitimately been ordained to the Episcopate by me in 1981, and all others whom they have in turn ordained bishops and priests, as well as their followers, to retract their error, leaving their actually false status, and reconciling themselves with the Church and the Holy Father, Pope John Paul II."
Sedevacantists deny the authenticity of this statement since it agrees with the 1975 Decree and 1983 Notification and ultimately invalidates their orders by Thuc's own admission.
This statement was reported in a variety of news sources including the United Press International. They also note that John Paul II lifted the excommunication of Thuc. https://www.upi.com/Archives/1984/12/17/Excommunicated-Vietnamese-archbishop-received-back-into-church/9212472107600/ There is no evidence that the men receiving "orders" have ever had the excommunication lifted.