It's a while since I've flown Singapore Airlines business class so I can't help you with that comparison. However I've just come back from a Munich to Bangkok/Chiang Rai to Zurich itinerary on Thai Airbuses and found them pretty good. Definitely much better than the last time I flew them about 6 years ago.

They're quite narrow seats but slope flat (if you know what I mean) but if you're on the large side you might find them uncomfortable.

I wouldn't rank them as high as BA as their seats are better or Air France as their food is better, but they were easily as good as KLM.

Not sure about whether the cost is good value for you as I'm not sure if that's a good fare.