The previous government of Thailand was increasingly undemocratic.

Lead by a billionaire businessman, the Burlusconi of SE Asia had bought
a significant number of the Senate. As an owner of most of the mass media
in his country he also bought influence over his compatriots and thwarted
democratic opposition. The extra judicial killing of over 3000 Thai civilians
on mere accusations of 'anti-social' behaviour for perceived populist gain
contravened basic human rights and international law.

The recent intervention, as far as I understand it, is a process of restoring
democracy to a land that had become a plutocracy. It's a very rare case
of a military coup to benefit the people, in my humble opinion.

... aren't all military coups justified by their perpetrators as "what the people want", or "so that we can restore democracy (later)"?

They ain't popular uprisings no matter how many yellow ribbons you tie on the gun barrel.