I, too, used Good Speed a couple of times and was happy with them. But I found Chi Chang in Promenada to be more convenient. My friend John doesn't speak Thai and had them build him a PC and recommend them. He said there was quit a bit of back and forth on selecting components.
I speak Thai and went to the same guy and we did the same thing. Though I first did lots and lots of research on https://www.invadeit.co.th/ and https://www.jib.co.th/web/ selecting parts from the case upward and outward. Then took the list to Chi Chang. They suggested a copy of H/W alternatives based on who they bought from and what is available and I came home and researched those. I found they met my criteria and that some were slightly more expensive and some were a little less. Did a great job. I have a great machine, cool, runs several photo processing S/W programs at the same time as well as the web and an email client. I am a happy camper.
Give them a try