I Need to buy men's large size shoes, rubber boots and sandels here in Chiang Mai or as near as possible.

I have a sized 13 Wide foot and can find nothing here.

Any Ideas?

will size 14 wide used work?

American or British size 13.

You almost have to go custom made, for big shoes here (13 & UP) I've been to this shop:

Dawood Leather Craft Shop

Sridonchai Road, Chang Klan, Mueang Chiang Mai, Chiang Mai, 50100

Tel: 053 392 891

and he makes custom shoes in many styles, in your exact, fitted size, for very reasonable prices.

Your other option is internet from US (Shoes XL or Zappos) and hope you don't get boned for customs duty.