National Office of Buddhism director Nopparat Benjawatananun said the selection process would not begin until the royal funeral rites for His Holiness, the 19th Supreme Patriarch, conclude on Jan 31. His Holiness passed away on Thursday, aged 100, as a result of a blood infection.
According to the process, the Sangha Supreme Council would nominate one of seven somdet phra racha khana _ the top-ranking senior monks in the Thai monastic hierarchy who hold the title of "Somdet" _ and forward the nomination to the prime minister, who will then submit the name to His Majesty the King.
"The decision is the prerogative of the King," Mr Nopparat said.
Section 7 of the Sangha Act of 1992 stipulates that His Majesty the King appoints the Supreme Patriarch.
The nominated somdet phra racha khana must be the most senior monk in terms of receiving the title of "Somdet" before the others, and the nomination must be endorsed by the Sangha Supreme Council, the clergy's governing body.
However, Mr Nopparat said the most senior somdet phra racha khana would not be nominated if he is unable to fulfil the duties of the Supreme Patriarch, such as through ill health.
In such an event, the next most senior somdet phra racha khana will be nominated instead.
Somdet Phra Maha Ratchamangalacharn, the 88-year-old abbot of Wat Pak Nam Phasi Charoen, is the most senior, having received the title in 1995.
The monk belongs to the Maha Nikaya sect.
The other six monks who hold the title, in descending order of seniority, are: Somdet Phra Maha Wirawong, 96, the abbot of Wat Samphanthawong of the Dhammayutti Nikaya sect who received the title in 2001; Somdet Phra Maha Muniwong, 86, the abbot of Wat Ratchabophit of the Dhammayutti Nikaya sect (2009); Somdet Phra Wannarat, 77, the assistant abbot of Wat Bowon Niwet of the Dhammayutti Nikaya sect (2009); Somdet Phra Buddha Kosacharn, 83, the abbot of Wat Suthat Thepphawararam of the Maha Nikaya sect (2010); Somdet Phra Thirayarnmuni, 66, the abbot of Wat Thep Sirin of the Dhammayutti Nikaya sect (2010); and Somdet Phra Buddha Chinnawong, 72, the abbot of Wat Pichaya Yatikaram of the Maha Nikaya sect (2011).
Maha Nikaya is one of the two major sects of Theravada Buddhism in Thailand.
Most Thai Buddhist monks belong to the sect, while the Dhammayutti Nikaya, which was founded by the King Rama IV, is considered more strict than the Maha Nikaya sect.
Traditionally, the Supreme Patriarch position alternates between the two sects.
The late Supreme Patriarch was of the Dhammayutti Nikaya sect.