My question to you is why do you want insulated (double-pane) windows?
Is it to reduce noise?...keep your home cooler?...other reasons?
I have a many year background of selling and installing replacement windows in the U.S., but when we built our home here in 2008, I came to understand that I really didn't need the extra expense of that type of window here. We are not in the city so noise was not a factor, and even though we do have air con for the house, we rarely feel the need to use it.
Proper size of windows (larger than most Thai homes), and good landscaping for trees and shade, allow us to have the windows open most of the time for good ventilation and cooling. The main house has 5 big windows (200 x 140) and 2 smaller (100 x 140), and the dining room has 3 large and one smaller.
Our window guy is the son-in-law of our neighbor and does excellent work, and his shop is in Prasat. Let me know if you would like to contact him.