This was the most pronounced in South Korea, because it is so advanced technologically but somehow still has that SEA feel of wanton medical incompetence. It catches you by surprise more.
Massive doses of antibiotics no matter what, IVs for no good reason, X-ray to check for head lice (!!)... fun stuff.
I heard medical care in Singapore and HK can be excellent though. Interesting to hear you've had such a good experience in Thailand, it was the opposite for us (GP, dental, surgical -- you name it, it sucked, even in ?top? places like the Bangkok Hospital). Where did you go?
I've had dental work at Bumrungrad, Bangkok Hospital and more recently been going to a small dental clinic near my home. Besides regular checkups and cleanings I had a redo of a root canal that was done in the US and went bad after moving to Thailand, got a new crown, and had some old fillings replaced - excellent care in all cases and particularly the dental clinic has the latest and greatest dental tech.
I have also been getting annual medical exams since moving here 15 years ago, at Bumrungrad, Phayathai, St Mary's Korat, and Bangkok Hospital (Korat and Pak Chong branches). They have always been routine and efficient. The weak spot is the consultation with the GP after all your results are in - some of them a pretty dopey and I would guess it is those guys that are going to be a bad experience if you see one of them for an ailment.
Those are all anecdotes, of course. YMMV.