Regent Phra Kiao Matu or Intramuli ruled Kyainge tong in 765 M.E (approximately 13th century A.D). He was the one who brought in Buddhism from Northern Thailand into Kyainge tong region but in 772 M.E a great fire broke out at a place called Hway Puun. Then a great drought also devastated the region. The Regent then called in the astrologers to predict the future and find ways to remedy the situation.

An astrologer named Aok ta ma explained that the region of Khun people of Kyainge tong is under the influence of the Monday planet and therefore to act against this bad influence a statute of a frog with the moon in its mouth, as well as some pagodas made of sand should be constructed near Nam Khun stream at the northwestern part of the town as offerings. The Regent followed the astrologer's advice and as soon as the ceremony concluded a huge thunder storm broke the long drought. The people were happy as they could now start their planting.

Since then this annual water festival called Sung Karn is celebrated at Kyainge tong according to the ancient custom.

However, the original festival contained some lewd elements. According to folklores of the region there was once a very beautiful but sexually very active princess. She was literally insatiable in her sexual appetite and many wars were fought on her account. When she died and because of her bad karma she became a female frog on the Nam Khun stream. Annually a festival was held at Kyainge tong to marry this frog princess with Sakra, King of the Celestial Beings to bring about good rains and consequently good harvest. The male revelers at this water festival carry around the town a wooden replica of the male penis. At the end of the ceremonies the wooden penis is inserted into the vagina of the frog and thus consummate the marriage between the frog princess and Sakra. The town people believe that this will bring good rains for a good harvest. No females were allowed to attend the festival, as it is so lewd and vulgar.

But in 1260 M.E, the ruler of Kyaing tong, Sao Kawn Kiao Intraleng prohibited this vulgar and lewd part of the ceremony by royal decree and ever since this practice had been discontinued. However, a traditional Gon Shan custom of celebrating the water festival is still being celebrated at Kyainge Tong annually.

Every year on a fixed date of the second week of April at 1.00 p.m the Nan Ta Pay Ree (Drum for Luck & Prosperity) is brought out from Wat Keng Zan to the ceremonial compound. Sand pagodas and a mud image of a frog are constructed on the bank of the stream. Then the image of Sakra riding on the appropriate animal for the given year is made with papier mache. By tradition Tai-Loi people from Mong Yang district (of Mon Sip Ha Yang Ngin) must beat this drum continuously for 24 hours. Then at 1.00 p.m next day the procession will start for Long Goap where the statue of the Frog princess and sand pagodas are waiting. Also by tradition a representative of the Zar family must ride a horse dressed as a Sakra and lead the procession to the ceremonial site by the stream. The ceremony ends with offerings made to the pagodas and "symbolic marriage" of the Frog princess with Sakra statue. All along the way people throw water on each other and enjoy the water festival.

After the ceremony the procession returns to town and on the way back 4 monks from Wat Zom Kham wait under the Bodhi tree at the center of the town to bless the revelers with holy water for happiness and prosperity in the coming year.