Chicago's Thomas Records was owned by former Impressions' manager, Eddie Thomas. He had his label distributed by various different labels and distributors at different times (Chess (along with Monk Higgins' labels) and Buddah (along with Curtis Mayfield's Curtom Records). I don't recall Eddie Thomas releasing any gospel.
As The Thomas Records which released The Thomas Singers is likely named after the group (rather than coincidentally after Eddie Thomas), I doubt that it is Eddie Thomas' label, but, rather a one-shot label used to release The Thomas Singers' records. So, I'd guess that it is a label likely to be located somewhere other than Chicago, otherwise, the owners would have used another name to avoid confusion with Thomas' label.