So what’s the deal with the Th.M.? How does it compare / contrast with an M.Div., or an M.A. in Theology? Do some religions tend toward the Th.M. than others?
Simply put (and others can elaborate if they wish): MDiv - “Professional “ degree that prepare individuals for a career in ministry. MA - Typically provides education in a specific academic focus. ThM - Typically requires an individual have a MDiv as it is seen as the minimum requirement to teach at Bible Colleges. Source: https://www.seminarycomparison.com/seminary-comparison-mdiv-vs-ma-vs-thm/
The ThM is generally a one to two-year post-MDiv program that is either treated like a terminal award which, as JoshD noted, qualifies the holder to teach (both undergraduate and graduate). Or, the ThM is an intermediary award earned on the way to a research doctorate. The only institution that I know of that offers a stand-alone ThM that is the full four-years (i.e., 120 credits) is DTS. Most post-MDiv ThM programs have a significant research element (either a thesis or perhaps a ministry project). Not really. In the Christian tradition, the MDiv is still the standard degree for the pastorate, mission field, or for parachurch leadership. The ThM is a step beyond. Interestingly, since the BDiv (or ThB) is the European equivalent of the North American MDiv, most European MA's in theology are structured exactly like an American ThM. For example, I have an MA from a UK University, which included a significant research thesis (half the program). Thus, if one wanted the "ThM experience" but did not possess MDiv or equivalence, a European or South African MA in theology might scratch the itch.
I’ve seen some folks label it as “S.Th.D.” I suppose this is to self-consciously signal something other than the potential scarlet letter confusion that could ensue by putting “S.T.D.” after one’s name.