www.phuketprison.th.org/
This is the website for Phuket Prison....if you can read Thai...but it certainly lists the address as in Phuket Town. Whether the new prison in Thalang (which I must admit I don't remember reading about, but the I'm not a regular Gazette Reader) is completed yet I'm not sure, but there was a temporary prison in Thalang a while ago. That maybe where she is.
The website seems to be up to date (ish)...it certainly annonunces the new Prisons Govenor.
Right....my wife has just translated a section of the website, and a footnote does say thet there is a temporary prison on 100 rai of land in Baan Bangjo, Amphur Thalang, why temporary I don't know, but it seems that Phuket Town is still the contactable address.
Of course building something as temporary is a good way to build poor quality...then keep it for years under that label.