Princess Sirindhorn of Thailand, the Princess Royal and the Princess Debaratana Rajasuda (, ; ; born April 2, 1955), formerly Princess Sirindhorn Debaratanasuda Kitivadhanadulsobhak (; ), is the second daughter of King Bhumibol Adulyadej and younger sister of King Vajiralongkorn. Thais commonly refer to her as "Phra Thep" (), meaning "princess angel". Her title in Thai is the female equivalent of the title once held by her brother, King Maha Vajiralongkorn. The Thai constitution was altered in 1974 to allow for female succession, thus making her eligible for the throne. Having been the eldest female child of the royal family (excluding Princess Ubolratana Rajakanya, who married a foreign commoner), her position is comparable to a princess royal. Early life Birth Sirindhorn was born on April 2, 1955, at Amphorn Sathan Residential Hall, Dusit Palace. The third child of King Bhumibol and Queen Sirikit. As the royal couple has only one son, the Thai constitution was altered in 1974 to allow for female succession. This made Sirindhorn second-in-line to the throne (after Vajiralongkorn) until the birth of Princess Bajrakitiyabha in 1978. Early education Sirindhorn attended Kindergarten, Primary and Secondary at Thailand's most exclusive school: The Chitralada School which was established for the children of the Royal Family and Palace staff. She ranked first in the National School Examinations in primary level (grade 7) in 1967, in upper secondary level (grade 12) in 1972, and fourth in the National University Entrance Examination in 1975. Higher education In 1975 she enrolled in the faculty of arts at Chulalongkorn University and graduated with a Bachelor of Arts, first-class honours and a gold medal in history in 1976. From 1976 she continued her studies in two graduate programs concurrently, obtaining a Master of Arts in Oriental epigraphy (Sanskrit and Cambodian) in 1980 and also archaeology from Silpakorn University in 1980. From October 1977, she studied Sanskrit in Bangkok for two years under the tutelage of renowned Sanskrit scholar Satya Vrat Shastri. In 1978, she obtained a Master of Arts in Pali and Sanskrit from Chulalongkorn University. In 1981 she enrolled in a doctoral program at Srinakharinwirot University, and was awarded a PhD in developmental education in 1987. In 1984 she earned a certificate from the Asian Regional Remote Sensing Training Centre at the Asian Institute of Technology where she studied for two months. In April 2001 she won a scholarship in Chinese culture at Peking