Hey, I'm having a really hard time finding clothes in Kunming that fit. Anyone know where to buy size 38 jeans, western xxl shirts and maybe this is impossible but size US 15 shoes? Any help would be appreciated. Cheers!

Luosiwan may be worth a try, but it might be a case for mail order, especially for the shoes.
Trousers, you need to find an export clothing company. A Chinese guy with 38 waist will still have no thighs and no butt. Trousers will be cut accordingly.
Marks and Spencer do uk sizes and mail order. Decathlon Sports do euro sizes and have hiking style clothes, but not jeans; however they do have large ( non-dress) shoes.
As a 38 you just might get lucky and find something at The Gap store, several branches in town. One at Golden Eagle Mall, one at Aegean Mall.

I am 38-40 and buy stuff when I travel to HK and Shanghai

Thanks for the information. I also was thinking Hong Kong or Shanghai would be a better option.
Cheers

Interestingly if you ever do see a Marks and Spencer's it is well worth paying a visit as all of their sale items are usually the bigger sizes.

When buying clothes online always ask if the size is European (欧码 OuMa) as you may find a Chinese large size is still too far.

Your best option is Taobao, or some of the shops around town with 外贸 in their signage.

Where is M&S in town?

I don't think there is one, but there's a few dotted around China.

If it might be within your budget, could also get quote from a tailor for clothes made to your measures.

The Silk Street Market in Beijing and Gongbei Underground Market in Zhuhai – 拱北地下广场, 珠海 has a lot of export clothing. Oddly. I found more and better quality winter clothing, coats and jackets, in Gongbei than in Beijing.

Thanks for all the advice.

2-3 years ago i bought a lot of larger size clothes at an outlet store on Wuxi road. It was on the east side between Renmin road and the Yunnan Hospital of Traditional Medicine. Not sure of name of store and not even sure if still there. Friend told me about the store and found it by looking through the doors of several stores. Had 40-42 waist pants in 34 length and a lot of XXL shirts.