As for your concern about Scoot not allowing your own food/drinks, I've yet to see an LCC actually enforce this, though I have heard of it. Keep drinks discreet and don't be terribly concerned regardless.

DMK sucks in terms of getting to/from Bangkok and doubly so international arrivals.

TG will likely be far more reliable in the event of irregular operations, they'll put you on another carrier (likely NH if available, otherwise something with a connection). Scoot will tell you to wait until they can get a plane to Japan, likely the following day or two.

TG certainly has nothing special in terms of IFE, so that's not much of an advantage over Scoot. Plan to have your own entertainment available regardless, you're looking at 12 hours in total round trip and TG may not have anything fresh you're interested in. Take a tablet loaded up with your own choice of movies, or even pre-upload them to your phone via USB if need be.

For myself, this would not even be a debate, it'd be TG without question, don't care if Scoot was cheaper or not. But in your case without *G status I can see the weighing of options. My question though, if you already have status on Skyteam, why not take the connection on MU or CI? Usually they run a pretty convenient schedule between Japan and SE Asia? I happily take connections over a direct flights to maintain my *G benefits when direct *A flights aren't reasonably priced/available.