Question: Who was appointed arbitrator by the first convert to the faith that is the most common religion in Southeast Asia?

Knowledge 1: Southeast Asia
Islam is the most widely practised religion in Southeast Asia, numbering approximately 240 million adherents which translate to about 40% of the entire population, with majorities in Indonesia, Brunei, Malaysia and in Southern Philippines with Indonesia as the largest and most populated Muslim country around the world. Countries in Southeast Asia practice many different religions. Buddhism is predominant in Thailand, Cambodia, Laos, Burma, Vietnam and Singapore. Ancestor worship and Confucianism are also widely practised in Vietnam and Singapore. Christianity is predominant in the Philippines, eastern Indonesia, East Malaysia and East Timor. The Philippines has the largest Roman Catholic population in Asia. East Timor is also predominantly Roman Catholic due to a history of Portuguese rule. [SEP] Knowledge 2: Umayyad Caliphate
Following this battle, Ali fought a battle against Muawiyah, known as the Battle of Siffin. The battle was stopped before either side had achieved victory, and the two parties agreed to arbitrate their dispute. After the battle Amr ibn al-As was appointed by Muawiyah as an arbitrator, and Ali appointed Abu Musa Ashaari. Seven months later, in February 658, the two arbitrators met at Adhruh, about 10 miles north west of Maan in Jordon. Amr ibn al-As convinced Abu Musa Ashaari that both Ali and Muawiyah should step down and a new Caliph be elected. Ali and his supporters were stunned by the decision which had lowered the Caliph to the status of the rebellious Muawiyah I. Ali was therefore outwitted by Muawiyah and Amr. Ali refused to accept the verdict and found himself technically in breach of his pledge to abide by the arbitration. This put Ali in a weak position even amongst his own supporters. The most vociferous opponents in Ali's camp were the very same people who had forced Ali into the ceasefire. They broke away from Ali's force, rallying under the slogan, "arbitration belongs to God alone." This group came to be known as the Kharijites ("those who leave"). In 659 Ali's forces and the Kharijites met in the Battle of Nahrawan. Although Ali won the battle, the constant conflict had begun to affect his standing, and in the following years some Syrians seem to have acclaimed Muawiyah as a rival caliph. [SEP] Knowledge 3: Identity of the first male Muslim
One account in Tabari says that the first male convert is Zayd ibn Harithah, a freed slave who had become Muhammad's adopted son. It is known that Ali is the first person to convert to Islam, however some dispute this arguing he was only 12 years old at the time he embraced Islam.
Knowledge 1: Southeast Asia
Islam is the most widely practised religion in Southeast Asia, numbering approximately 240 million adherents which translate to about 40% of the entire population, with majorities in Indonesia, Brunei, Malaysia and in Southern Philippines with Indonesia as the largest and most populated Muslim country around the world. Countries in Southeast Asia practice many different religions. Buddhism is predominant in Thailand, Cambodia, Laos, Burma, Vietnam and Singapore. Ancestor worship and Confucianism are also widely practised in Vietnam and Singapore. Christianity is predominant in the Philippines, eastern Indonesia, East Malaysia and East Timor. The Philippines has the largest Roman Catholic population in Asia. East Timor is also predominantly Roman Catholic due to a history of Portuguese rule. [SEP] Knowledge 2: Umayyad Caliphate
Following this battle, Ali fought a battle against Muawiyah, known as the Battle of Siffin. The battle was stopped before either side had achieved victory, and the two parties agreed to arbitrate their dispute. After the battle Amr ibn al-As was appointed by Muawiyah as an arbitrator, and Ali appointed Abu Musa Ashaari. Seven months later, in February 658, the two arbitrators met at Adhruh, about 10 miles north west of Maan in Jordon. Amr ibn al-As convinced Abu Musa Ashaari that both Ali and Muawiyah should step down and a new Caliph be elected. Ali and his supporters were stunned by the decision which had lowered the Caliph to the status of the rebellious Muawiyah I. Ali was therefore outwitted by Muawiyah and Amr. Ali refused to accept the verdict and found himself technically in breach of his pledge to abide by the arbitration. This put Ali in a weak position even amongst his own supporters. The most vociferous opponents in Ali's camp were the very same people who had forced Ali into the ceasefire. They broke away from Ali's force, rallying under the slogan, "arbitration belongs to God alone." This group came to be known as the Kharijites ("those who leave"). In 659 Ali's forces and the Kharijites met in the Battle of Nahrawan. Although Ali won the battle, the constant conflict had begun to affect his standing, and in the following years some Syrians seem to have acclaimed Muawiyah as a rival caliph. [SEP] Knowledge 3: Southeast Asia
There are several theories to the Islamisation process in Southeast Asia. Another theory is trade. The expansion of trade among West Asia, India and Southeast Asia helped the spread of the religion as Muslim traders from Southern Yemen (Hadramout) brought Islam to the region with their large volume of trade. Many settled in Indonesia, Singapore, and Malaysia. This is evident in the Arab-Indonesian, Arab-Singaporean, and Arab-Malay populations who were at one time very prominent in each of their countries. The second theory is the role of missionaries or Sufis.[citation needed] The Sufi missionaries played a significant role in spreading the faith by introducing Islamic ideas to the region. Finally, the ruling classes embraced Islam and that further aided the permeation of the religion throughout the region. The ruler of the region's most important port, Malacca Sultanate, embraced Islam in the 15th century, heralding a period of accelerated conversion of Islam throughout the region as Islam provided a positive force among the ruling and trading classes.
Knowledge 1: Southeast Asia
Islam is the most widely practised religion in Southeast Asia, numbering approximately 240 million adherents which translate to about 40% of the entire population, with majorities in Indonesia, Brunei, Malaysia and in Southern Philippines with Indonesia as the largest and most populated Muslim country around the world. Countries in Southeast Asia practice many different religions. Buddhism is predominant in Thailand, Cambodia, Laos, Burma, Vietnam and Singapore. Ancestor worship and Confucianism are also widely practised in Vietnam and Singapore. Christianity is predominant in the Philippines, eastern Indonesia, East Malaysia and East Timor. The Philippines has the largest Roman Catholic population in Asia. East Timor is also predominantly Roman Catholic due to a history of Portuguese rule. [SEP] Knowledge 2: Umayyad Caliphate
Following this battle, Ali fought a battle against Muawiyah, known as the Battle of Siffin. The battle was stopped before either side had achieved victory, and the two parties agreed to arbitrate their dispute. After the battle Amr ibn al-As was appointed by Muawiyah as an arbitrator, and Ali appointed Abu Musa Ashaari. Seven months later, in February 658, the two arbitrators met at Adhruh, about 10 miles north west of Maan in Jordon. Amr ibn al-As convinced Abu Musa Ashaari that both Ali and Muawiyah should step down and a new Caliph be elected. Ali and his supporters were stunned by the decision which had lowered the Caliph to the status of the rebellious Muawiyah I. Ali was therefore outwitted by Muawiyah and Amr. Ali refused to accept the verdict and found himself technically in breach of his pledge to abide by the arbitration. This put Ali in a weak position even amongst his own supporters. The most vociferous opponents in Ali's camp were the very same people who had forced Ali into the ceasefire. They broke away from Ali's force, rallying under the slogan, "arbitration belongs to God alone." This group came to be known as the Kharijites ("those who leave"). In 659 Ali's forces and the Kharijites met in the Battle of Nahrawan. Although Ali won the battle, the constant conflict had begun to affect his standing, and in the following years some Syrians seem to have acclaimed Muawiyah as a rival caliph. [SEP] Knowledge 3: Black people
The Negritos are believed to be the first inhabitants of Southeast Asia. Once inhabiting Taiwan, Vietnam, and various other parts of Asia, they are now confined primarily to Thailand, the Malay Archipelago, and the Andaman and Nicobar Islands. Negrito means "little black people" in Spanish (negrito is the Spanish diminutive of negro, i.e., "little black person"); it is what the Spaniards called the short-statured, hunter-gatherer autochthones that they encountered in the Philippines. Despite this, Negritos are never referred to as black today, and doing so would cause offense. The term Negrito itself has come under criticism in countries like Malaysia, where it is now interchangeable with the more acceptable Semang, although this term actually refers to a specific group. The common Thai word for Negritos literally means "frizzy hair".

Answer: Abu Musa Ashaari