I am actually in Bangkok now and picking up 4 suits and 2 jackets from WG in all seasons place-all fully canvassed. However I am a customer of 10 years standing who gives them 200,000 Bhat worth of business a year for the last 10years and have done many many referrals. It is well possible they don't want headache and extra labour of full canvas for new walk in customers.
. Btw usd300 is not the price for a suit- just tailoring. You have to get your own fabric.