I am foreigner here as well who moved to sofia just few months ago and I enjoy reading your blog very much. 
I love Thai food so much. I googled Thai food restaurant in sofia and came across your blog. I will defenitry try PUZZLE soon. 
Have you tried the restaurant 'Pacific'? It's a Asia food restaurant which offers Japanese, Korean, Indonesia, Thai and others. I didn't try many foods there but PadThai was good! Recommended:)