609 Bedtime Story at 11 episodes is an exception, and I postulate that one reason for the exception is that it utilizes fantasy rules.
The rules are ostensibly scientific, but the overall premise is more magic than science. Two young men share the same apartment in different universes. The universes only connect for an hour a night. And they operate in reverse order, so Mum visits Dew's universe at the end of their relationship--and sees him shot to death. He then visits Dew over a month until Dew meets him for the first time.
In the meantime, the time in each universe proceeds forward.
It is less confusing than it sounds--unless one tries to make sense of the time factor, which I don't recommend. I would have to watch the series many more times to check if the writers were consistent.
In any case, they make no glaring errors, and the attempt to stick to the rules--so (1) Mum and Dew know each other to a differing degree in each episode and (2) even though the end is in the beginning, Mum doesn't figure out the end--the murderer--until his time catches up to Dew's time--forced discipline onto the story.The episodes do not suddenly throw in crazy parents and an excess of minor rivals to keep the series going an extra four to five episodes. The episodes have to link up.
Truth is, 609 Bedtime Story isn't my favorite Thai paranormal series. That would be Dear Doctor. But 609 Bedtime Story has fewer story writing flaws than many other series. It also showcases some fairly impressive acting with strong character payoffs.
In regards to the writing, the rules helped.
(I will address the problem of "cloning"--falling in love with a character who is not the character--at a later date.)