King Mohnyin Thado formally ascends to the throne of Ava.

Mohnyin Thado was king of Ava from 1426 to 1439. He is also known in Burmese history as Mohnyin Min Taya after his longtime tenure as the sawbwa of Mohnyin, a Shan-speaking frontier state. He founded the royal house of Mohnyin that would rule the kingdom until 1527.

The Ava Kingdom also known as Inwa Kingdom or Kingdom of Ava was the dominant kingdom that ruled upper Burma (Myanmar) from 1365 to 1555. Founded in 1365, the kingdom was the successor state to the petty kingdoms of Myinsaing, Pinya and Sagaing that had ruled central Burma since the collapse of the Pagan Kingdom in the late 13th century.

May 20 is the 140th day of the year in the Gregorian calendar; 225 days remain until the end of the year.