Does anyone know where I can buy rush matting in Chiang Mai similar to the one in the image? I need something at least 2m x 2m but preferably a bit larger. I am also looking for the cheapest place to buy lots of cushion fillers. I want to buy about 20.

Thanks in advance for any suggestions!

I think you will have a hard time finding something like that in Chiang Mai, but if you do, please post where you found it. I went looking several years ago and struck out. Baan and Beyond has small durable mats 1m by 1.5m, but nothing bigger. Index used to have them, but no more. I finally ended up having a friend buy something at IKEA and ship it to Chiang Mai. I bought this 2m by 3m rug/mat and have had it for several years. It's reversible.

http://www.ikea.com/th/en/catalog/products/50166413/#/00166415

Yup, IKEA has exactly that. Bangkok only though.

Cushion filler (kapok) at Warrorot Market, they sell it in big bags (smaller bags too if you're only making one for the sofa). If you're looking at big quantities, I'd suggest using sheet foam cut to size and kapok on top sides and bottom to give plenty of support but still a cushion feel. Would be significantly cheaper too I imagine.