Complex sentence: According to the Wat Burapharam Inscription, Mahathammaracha II abdicated and entered the monkhood in 761 LE (1942 BE, 1399--1400 CE) and appointed his wife, Queen Si Chulalak, as the regent of Sukhothai.
Split into simpler sentences: According to the Wat Burapharam Inscription, Mahathammaracha II abdicated and entered the monkhood in 761 LE (1942 BE, 1399--1400 CE). Before becoming a monk, he appointed his wife, Queen Si Chulalak, as the regent of Sukhothai.