A bit late to reply, but I'll comment what I know for information. Firstly, the set of images shown here is basically an erotica, so shouldn't be taken as depicting the real historical form of punishment.
Chosun - the name of the Korean dynasty depicted in the picture - used penitentiary practices imported from Ming Dynasty of China, and it was a highly standardized system which included various forms of corporal punishments.
When it comes to paddling, the system defined several different types of such punishment depending on the severity of the crime. What was depicted in the images is one of such types which was, however, used in a limited fashion to punish more severe crimes like a military insubordination.
The form more widely used for civillian criminals involved using straight and smaller paddles, or floggers, depending on severity of the crime. They could administer paddling from 60 to 100 times using a wooden paddle of a specified size.
And when it was administered to a female criminal, she was allowed to wear an equivalent of an underwear, except for the case of adultery. And they would usually pour water upon the underwear, but according to an article I'm reading, it was to prevent it from being turned up to reveal the private part during the punishment, rather than to make it more humiliating for the woman.