This is Pra Lor and his two girlfriends. He's a prince; they're princesses from a neighboring place and, you guessed it, their king fathers don't get along. But they find a way to live happily together, and the girls both get pregnant, which is Thai code for, yes, they were all doing it.
They get discovered in the fullness of time and killed with arrows, stuck together with the arrows in a standing position, makes a better picture I suppose.
These really downbeat stories are very common in Thailand.
This painting is in a temple, even displaying clearly, as it does, the secondary-sexual-characteristics of the girls.