I am rather somewhat rotund and have trouble buying shirts that actually fit me but its also due to the fact that i'd like to buy some shirts that arn't the obilgatory "check pattern". My thinking was to be able to select a material other than "check", i'm getting rather tired of it.

Opposite the old klang plaza is a huge shop with hundreds of materials. The ladies there can show you suitable ones for shirts or trousers and give you the right amount, if you're an xxl probably around 2m - 2.5m of material.

Take it to one of the many tailor shops, and all in, it should be around 1,000 baht for a tailored shirt of the material you choose.