An autopsy concluded that the body was then dismembered in the laundry room with a jigsaw, knife and garden shears.
Body parts were then chopped up with a hand blender, 'pureed' and dissolved in a chemical solution, local outlet Blick reported.
A medical-forensic report also 'contradicts his description of self-defence', according to Swiss outlet FM1 Today.
Thomas, who is a Swiss national, was reportedly arrested a day after her remains were found by a 'third party'.
Friends expressed their shock at the news. One told Blick as the news broke: 'To me, they seemed like the perfect family.'
The couple, who got married in 2017, lived overlooking scenic views from a 'spacious semi-detached house' in an affluent area of Basel, 20 Minuten reported.
Another said the relationship had been 'in crisis for months', with police allegedly called out beforehand over reports of physical violence.