The six included Porntip Jala, former secretary-general of the Council of State, Narongchai Akaraserani, an adviser to the National Council for Peace and Order (NCPO), and Pradit Wannarat, rector of the National Institute of Development Administration.
The only appointee who has yet to report for duty is Som Jatusripitak, a former appointed senator.
He had formally informed the Office of the Senate Secretariat that he is still on an overseas trip and would report in on Aug 7, in time for the opening of the NLA by His Royal Highness Crown Prince Maha Vajiralongkorn.
Of the original 200 appointed members, the NLA now has only 198 members, as two of them have been taken off the list.
Lt Gen Thawatchai Samutsakhon, former 2nd Army commander, formally resigned on Monday due to a qualification problem. Aziz Pitukkumpol, the Chularatchamontri, has also sent a letter announcing he will not accept the seat because it would conflict with his religious duties as the Muslim spiritual leader in Thailand.
Senate secretary-general Norarat, the acting NLA secretary-general, said all is ready for the NLA's opening ceremony on Aug 7. The first NLA meeting on Aug 8 would elect the NLA president and two deputies.
She denied a report the NLA would vote to endorse the new prime minister next week. This has not yet been scheduled, pending a royal command appointing the NLA president and deputies.
Mrs Norarat said the meeting regulations of the NLA of 2006 would be initially used for the meeting. After the election of the NLA president and deputies, the NLA would set up a committee to draft new meeting regulations.
The senate secretariate had already prepared draft regulations that could be used right away if approved by the NLA, she said.