I thought it was:
Aii, yiii, yi yiii
In China they do it with Chili
So here comes another verse
That’s worse than the other verse
Waltz me around by my willie!
I hate to talk about your momma but she’s in my class
She’s got popcorn titties and a rubber ass
She’s 99
She’s Frankenstein
She’s the fattest motherfucker on the welfare line.
Damn, we was some pottymouthed 7 year olds.
Yeah, best way to deal with insults like that is to turn them around.
“Your mother sucks cock…FOR MONEY.”
“No, she doesn’t - she sucks cock for CRACK. She has a REGULAR job for the money, duh.”
Wow, you sure showed him.
You suck!
And I swallow too, what’s your point?
Your momma sucks!
Too bad your mom didn’t.
Hey, it’s bad enough some guy insulted the OP’s mom. Now you’re making fun of his grammar. 
Ha, I just got that, -thanks.
I would have followed up with a “yeah, well your mom bukkakes, gargles with it and then swallows it.”
Then wait till the kid gets busted for looking up ‘bukkake’ sites on the internet by his swallowing mom.
There’s no swallowing in bukkake. Didn’t your mom teach you anything?
Fer da chissake!
That’s why I used commas. And even an itallicized then.
I really didn’t know that, thanks for the info. 
And that, in turn, will get the person who did the deed arrested and charged with battery or worse. Has the OP never even so much as seen an episode of COPS? It’s highly unlikely that there’s a jusrisdiction in the country where it is legal to physically attack someone over a verbal insult, even if it happens to be about your crack-smokin, john-blowin’ ho of a mother.
Anyway, I’m really enjoying the responses to this thread. Sorry mine isn’t up to the standards of wit displayed so far. Do carry on.
and I always thought it was:
Aii, yiii, yi, yiii
In China they never grow Chili
So sing me a verse that’s worse than the first verse
make sure that it’s foolish and silly…
O.K., this is bugging me. I let it go the first time, but these rhymes don’t fit the song. They don’t have the same number of syllables.
Besides, this one’s better:
Yo’ momma, yo’ daddy
Yo’ bald-headed granny
Got holes in her panties
from sittin’ on her fanny
Got a big behind
like Frankenstein
goin’ beep beep beep
down Sesame Street
Make it clear that you do not appreciate such childishness. Firmly tell him:
Dude, get OFF of my mother.
I mean, come on, I got off of your mother.
WAH! He made fun of my mom! WAH!
YOU: You suck!
HIM: Your mother sucks, for money!
YOU: Yeah, but not nearly as good as your father!
Or next time your phone rings when he’s around but the caller already hung up start a fake conversation with the phone: “Hello? Yes. I’m wearing jeans and a t-shirt why? You want to do what to me? That’s gross. With your tongue? You don’t even know me. For free? Well, I’ll think about it. Yeah, he’s right here hold on.” Hand the phone to your friend and say “Dude, it’s your mom.”
Honey, your mom doesn’t suck for money.
But she takes it in the hienie. :wally
HEY HEY HEY HEY HEY!!! HOW DARE YOU???
I’d like to go out on a limb and defend ieatglue’s mother.
She’s definately not 99.
ieatglue’s momma is so fat, her belt size is “Equator!”
ieatglue’s momma has so much hair under her arms, it looks like she’s got Buckwheat in a headlock!
ieatglue’s momma is so ugly, the weather satellites won’t photograph her hometown unless it’s cloudy!
I suspect that by now ieatglue has lost interest and gone back to his XBox.
Aiii, yiii, yi yiiii
Your grandmother swims after troop ships!
(taking it to the next level)