Assistant army chief Gen Paiboon Khumchaya, head of the NCPO's office of legal affairs and justice process, said he believed the interim constitution would take effect this month as earlier predicted by NCPO chief Prayuth Chan-ocha.
Establishment of a national legislative assembly would follow in August and appointment of the prime minister and cabinet ministers in September, he estimated.
Gen Paiboon declined comment on whether Gen Prayuth would serve as prime minister, He also said the question of whether martial law would be lifted after the cabinet is named has not been discussed.
Gen Paiboon said Gen Prayuth was satisfied with cooperation from all sides during the past 50 days.
In a survey by the Suan Dusit Poll, the public gave the NCPO an 8.82 out of 10 rating for its first-month performance. Gen Paiboon said Gen Prayuth wanted to see a score of 10.