There is an Aluminium shop on Thani road just little bit after Siam Commercial bank on the right side.
Also there is a shop on Bulamduan road after you pass the curve before Ploy resort on the left side.
Ask the locals when you arrive the place.
PVC doors selection can be found at 'Home Mega Mart' which is located on the ring road before Thep Nakhon hotel and 'Home Mart' which is located on Jira road before 'Taweekit' supercenter.
Anyway you can ask the big shops I mentioned above and they can advice one of their own contacts than you can compare prices.
Good luck with it.
