I think you are right. The reason eg BA hasn't prioritised reinstatement of flights to BKK is because it's a tourist only route without a decent number of higher fare seats in first or business.
So - as Thai's mission is principally to bring tourists to Thailand it ought to operate as a bucket cheap airline - like a long-haul Ryan Air. But that would be unpalatable for a brand bearing "Royal" in its name - with all the high salaried top-heavy management and hangers-on. So it is destined to fail.