(Thai: รามคำแหง, pronounced [rāːm kʰām hɛ̌ːŋ] ⓘ) or Pho Khun Ramkhamhaeng Maharat (Thai: พ่อขุนรามคำแหงมหาราช, pronounced [pʰɔ̂ː kʰǔn raːm kʰam hɛ̌ːŋ má hǎː râːt] ⓘ) was the third king of the Phra Ruang Dynasty, ruling the Sukhothai Kingdom (a historical kingdom of Thailand) from 1279 to 1298, during its most prosperous era.

[1]: 196  After his father's death, his brother Ban Mueang ruled the kingdom, assigning Ramkhamhaeng control of the city of Si Satchanalai.

The commoner would found the Burmese Hanthawaddy Kingdom and commission compilation of the Code of Wareru, which would provide a basis for the law of Thailand used in Siam until 1908,[6] and in Burma to the present.

The Thais also expanded south towards the Malay Peninsula, the History of Yuan mentions “since the people of Sien and of Ma- li-yü-erh have long been killing each other and are all in submission at this moment, an imperial order has been issued telling the people of Sien: do no harm to the Ma-li-yii-erh and hold to your promise.“[10] However, in the mandala political model, kingdoms such as Sukhothai lacked distinct borders, instead being centered on the strength of the capital itself.

[11] According to the Chinese History of Yuan, King Ramkhamhaeng died in 1298 and was succeeded by his son, Loe Thai, though George Cœdès says it is "more probable" it was "shortly before 1318".

[1]: 206–207  Sukhothai for centuries was the major exporter of the ceramics known as "Sangkhalok ware" (Thai: เครื่องสังคโลก) to countries such as Japan, the Philippines, Indonesia, and even to China.

The reverse of the 20 Baht note (series 16), issued in 2013, depicts images of the royal statue of Ramkhamhaeng seated on the Manangkhasila Asana Throne and commemorates the invention of the Thai script by the king.