Maha Sura Singhanat
Somdet Phra Bawornrajchao Maha Sura Singhanat was the younger brother of Phutthayotfa Chulalok, the first monarch of the Chakri dynasty of Siam. As an Ayutthayan general, he fought alongside his brother in various campaigns against Burmese invaders and the local warlords. When his brother crowned himself as the king of Siam at Bangkok in 1781, he was appointed the Front Palace or Maha Uparaj, the title of the heir. During the reign of his brother, he was known for his important role in the campaigns against Bodawpaya of Burma.
Bunma was born in 1744 to Thongdee and Daoreung. His father Thongdee was the Royal Secretary of Northern Siam and Keeper of Royal Seal. As a son of aristocrat, he entered the palace and began his aristocratic life as a royal page. Thongdee was a descendant of Kosa Pan, the leader of Siamese mission to France in the seventeenth century. Bunma had four other siblings and two other halfsiblings. Bunma himself was the youngest born to Daoreung.
Source: Wikipedia