Prime Minister Prayuth Chan-ocha, the NCPO and Army chief, will restructure the junta by appointing new members to it, the source said.
Five NCPO members will retire in September – Prayuth, Supreme Commander General Tanasak Patimapragorn, Navy chief Admiral Narong Pipatanasai, Air Chief Marshal Prajin Junthong, and Pol General Adul Saengsingkaew.
The five will not have the authority to issue orders in their agencies after their retirement, the source said.
Prayuth will appoint new military top brass to the NCPO as replacements to ensure it maintains its position and continues to have the support of the military.
The restructuring will help bring about solidarity and prevent conflicts in the military, according to the source.
Apart from military officials, civilians who will be appointed to the NCPO include legal expert Meecha Ruchuphan, former chairman of the previous National Legislative Assembly, and Somkid Jatusripitak, who will be in charge of foreign affairs.
Prayuth had wanted to appoint Somkid to the Cabinet but he is not qualified to be a minister after he was stripped of his political rights when the Thai Rak Thai party was disbanded, the source said.
Prayuth has decided to appoint Somkid to the junta to make use of his expertise, bringing the total number of NCPO members to 14.
The current interim charter limits the number of NCPO members to 15.
The NCPO will move its office from the Royal Thai Army headquarters to Ban Phitsanulok.