Songtham (Thai: ทรงธรรม, pronounced [sōŋ.tʰām]) or Intharacha III was the King of Ayutthaya from 1610/11 to 1628 of the House of Sukhothai.

His reign marked the prosperity of the Ayutthaya kingdom after it regained independence from Toungoo Dynasty, and saw the commencement of trade with foreign nations, especially the Dutch and the Japanese.

He was in the priesthood for 8 years before government servants asked him to leave and ascend the throne with the title Phrachao Songtham at the age of 29.

[5] Prince Chula Chakrabongse states, "the king went insane before he died...His younger son, who had killed the elder brother when their father was alive but helpless, now seized the throne."

[7] From Songtham onwards, Ayutthayan kings paid annual respect to the Buddha's Footprint in a grand river procession.

In 1621 he himself led Siamese armies into Cambodia to bring the kingdom under control but was repelled by King Chey Chettha II of Oudong.

[4]: 207–208 The English first arrived aboard the East India Company ship Globe in 1612, delivering a letter from King James I.

[9] The Portuguese, however, were treated alike and all the Iberians were technically disgraced from Siam after nearly a hundred years of royal support.