As Delia approached, Ash backed up slowly as he tried to get some distance away from his mom. “M-Mom, what are you doing?” He asked before she lunged. It was too late. She undid his belt and soon the pants were pooled at his feet, revealing a pair of yellow briefs with Pikachu’s face on the seat. “Mom!” He yelled right before the first swat fell, making him shift. Dawn was loving this as she busted out in laughter

Delia made a mental note of how many times that girl was making fun of her son. She would have regretted that, once it would have been her turn.
But first she wanted to focus on Ash, and so she gave him hef full attention.
"It's clear that you need some discipline put back in you, and I'm here for that." she said, sitting down on a near log and grabbing his wrist.

“M-Mom! This is not funny!” Ash blushed madly as he stumbled out of his pants, blushing madly as he was fighting to keep himself away from the log. Delia’s superior strength overwhelmed him as he was dragged effortlessly and even tripping to fall over her lap, showing off his embarrassing seat to Dawn, who was laughing hysterically. “Nice undies! Soooo cute!”

Delia slapped Ash's behind, saying firmly "It's a spanking, it's not supposed to be funny. Naughtiness has consequences, young man."
She began to slap him on his Pikachu's undies, with quite firm slaps given with a slow pace. She wanted to give him the time to elaborate every slap tha fell on his behind before the next one.

Ash had no time to protest as the spanks rang throughout the forest, causing the nearby Swellow to scatter and fly off into the distance. The trainer was already so upset that this situation was happening, he angrily tried to block the spanks with his hand. “Enough!”

Delia wasn't pleased with that reaction: he was supposed to accept his punishment like a good boy, not to react like a brat.
She grabbed his wrist and pushed it against his back, and resumed with the spanking.
"Don't block! Naughty boy!" Delia scolded.
She gave him just four swats, however, before stopping and usinng her hand to take his underwear down at his ankles.

“Ow! Gah! Ow! Ow! Nooo!!” Ash protested as he took the 4 swats before his underwear was yanked to his ankles, baring his pink hued butt for all at the camp to see. Dawn blissfully pointed and laughed at Ash as he was exposed in such a way. “Take your spanking like a good boy, Ash!”

Once the boy was bare bottomed, Delia resumed with the spanking. She really wanted to make that pink behind deep red, so he could learn to never disrespect his mother again.
To make sure she could make an impression, she began to aim on the sit-spots exclusively, while taking count of every time that girl was making fun of the situation.

Ash was kicking his feet wildly as he yelped out with each swat that fell on his backside, kicking so hard that his underwear was about to be kicked off his ankles. Tears already welling up in his eyes as his mom was all business, turning his butt redder and redder by the minute. Dawn had no idea what Delia was planning so she continued. “Maybe I should spank you next after all the times Pikachu shocked me!”

Delia delivered some extra hard swats, scolding him "You let your Pikachu shock this girl? What a naughty trainer! Pokémons misbehave when their trainers do!"
She spanked him some more, then finally stopped after having delivered a last very hard spank in the middle of his bottom.
"Done." she said "You can go to face a tree, with hands on your head. No talking, no moving, no rubbing."