This Hmong folktale is called, Xyooj Mim & Xyooj Kaub. It is very similar to the story, Ntsuag thiab Niam Nkauj Zuag Paj. The difference is in the opening's details.
Unfortunately, I do not have time to write the story down in Hmong so I am providing the audio clip only. For those of you who may not understand the Hmong language, here is a summary.
Xyooj Mim and Xyooj Kaub are a pair of orphaned siblings. One day, Xyooj Mim chances upon a dragon prince who offers her marriage and in return, he promises to give her brother a magic rice grain and a piece of meat that could replenish itself to feed the young Xyooj Kaub for the rest of his life. But the catch is that Xyooj Kaub must never completely eaten all his rice and meat. If he empties the food, it can never replenish itself again. Once grown, Xyooj Kaub's curiosity causes him to break the magic food spell, and he is left hungry once more.
While crying beside a lake, he stumbles upon the dragon king who offers Xyooj Kaub food and directions to find his sister, Xyooj Mim. To repay the dragon king's generosity, all he asks of Xyooj Kaub is to relay a message to his dragon king-in-law to come help rebuild his fire-damaged kingdom.