"Monster Next Door" is one of those gentle and soft romance dramas that are more about two people of opposite characters slowly getting closer to each other and finding a good balance in their relationship than it is about external conflicts.
As such, it can be either comforting or boring, depending on the personal taste and mental state of the viewer.

The tl;dr:
1. Is it good? -- It's certainly in the upper third of this year's Thai BLs, but it's not top-tier -- the overall production quality is good, acting is solid, and here are little to no plot holes. Regarding flaws, see below.
2. Did I like it? -- Yes, I enjoyed it immensely. I chose a time when I was in the mood for a light watch, with a soft and gentle couple, and this hit the spot. More on that, see the paragraph directly below this one.
3. Do I recommend it? -- I do. But only for those who are looking for a gentle low-stakes love story, where nothing hurts (much, or not for long), that has mostly but not only fluff.


I love how the drama shows us a couple who resolve their problems with open communication and gentleness, and try to understand and accommodate each other.
Park and Big represent their roles well -- one is more reserved and sometimes you have to look closely to understand how he feels, while the other telegraphs everything. The supporting friend group is hilarious, and both couples' stories fit well within the plot. I like the sets, the use of colours -- and even the opening song grew on me.
I very much liked it as a stress reliever and diversion from work and life, the drama is perfect for that.

(As an aside for those who have not watched this yet or were confused: Near the end of epiosde 1, God asks Diao to become คนคุยกัน /khon khui gan/, literally "people who talk with each other" -- it's translated as "dating" in the subtitles, which gives a wrong impression. /khon khui/ are two people who will meet up often, "talk" with each other, to get to know each other, with the prospect of a romantic relationship at a later stage. I don't think Western cultures have this exact same thing, so it's really hard to find an expression for it in English.)


Coming back to the drama; even if I like it a lot, there is one major and some minor irritants.

The one major irritant is Khun Shy's living conditions. Khun Shy is Diao's much beloved turtle -- for him, Diao even asks his neighbour for help, even if he doesn't quite trust him at this point. So, apart from the fact that it hurts every time we have to watch Khun Shy desperately trying to escape his prison, it also does not make any sense within the story that his cage is so small.
Everything else in both Diao and God's rooms is lovingly chosen and presented by the production team -- these rooms represent their owners in style, displayed items and colour scheme. Why then, is this not true for Khun Shy? Diao's love for him should have been reflected in the turtle's living condidtions. You can't tell me that someone like Diao, who has been obsessed with turtles his whole life and loves his own little turtle very much would *not* dedicate at least half his living space to a luxurious habitat for Khun Shy?!
It is a grave mistake on the side of the production team that they did not see this.

There are a few minor irritants that could have been avoided with a few more passes over the script and the editing -- the whole drama does not feel as polished as it could have been. Quite a few of these things I have also seen in other Thai BL production, so "Monster Next Door" is not alone in this. But given the care the drama shows in other aspects, it's a pity that these little splinters are left.

What follows now is what the Germans call "Meckern auf hohem Niveau" -- "complaining on a high level". When something is well done in comparison to other similar things, it's sometimes even easier to point out remaining flaws; to wish that something good could be even better, if not perfect. So, yes, even if the following text got quite long, the flaws really ARE minor.

I'll just list a few examples, to make my point clearer (some spoilers ahead!):
* There are many smaller excellent ideas. For example, the "angel" and the "devil", who represent the "introverted" and "extroverted" character traits. Or that Diao posts his thoughts on a private profile, so that nobody will see them. Similarly, the use of the MBTI types -- only seen during the opening scenes and mentioned once later in the drama, but later it doesn't play any role. All of these cute ideas are discarded as soon as they are no longer useful (or forgotten by the writers?) -- I'd have liked to see a resolution or a more continuous use for them.
* Passing of time is often unclear. How many days passed between God and Diao's agreement to become /khon khui/and the next step in their relationship? How often did they talk on the balcony during that time? Must have been often enough that God found it necessary to buy a bell so Diao can call him -- and often enough that God knows a turtle motif will please Diao -- but these scenes are never shown, and if viewers don't pay attention then they might be a bit confused. (A similar thing happens after Diao loses his bracelet.)
* God (whose name is short for "Godzilla") is repeatedly and consistently the "monster", it's even in the title. I think they should have explored this more and deeper, have him consistently be a bit too loud, a bit too large, a bit too much. Instead, they chose to add the "God is like a dog" simile -- while it does fit, it's too much for one character.

Sometimes less is more, and I think it would have been better for the writing team to go over their script two or three times more to cut everything that is not necessary to the story (there are some scenes that don't add anything) and instead explore some of the themes in more detail.

For example, God accuses Diao in a later episode that he doesn't know anything about him -- but what do we know about God? What made him the way he is? Where does his need to be a "good boyfriend" come from? Why does he obviously need to prove his worth by providing for and servicing his Diao?
As it is, God is more the stereotypical "green flag boyfriend" / "good seme", a fantasy boyfriend for the (female) audience, rather than a three-dimensional character. I think the drama would have gained from more background for him.
(Maybe leave out the secondary couple -- that one had such an interesting story, and there must be more to Wan's need for security and desire that things stay the same as always, which was already there before Tan left. Those two would have deserved their own story.)

Related to that, I would have liked the drama to break out more from the "top/bottom" mold. They had the best starting point -- an introvert and an extrovert who will have to find a balance between their needs.
Why not cast the smaller man in the "extrovert" role of God and vice versa? Why not let the smaller and introverted Diao top God, at least let him "top from the bottom", instead of letting him slide back into the passive "uke" role in bed?
We got a good story about character growth, and Diao has always been straightfoward and strong when it comes to stating his own needs and wants (even in times when he needs to process and think, he usually makes it very clear). We got a beautiful story about a couple that has to find their own way, so both of their needs are met. Why not reflect that when they are physically intimate?

This is what I mean when I say "the whole drama does not feel as polished as it could have been". There are quite a few missed opportunities, and that's a shame when this is a drama that is quite good overall.
I think, on the whole Thai BLs have been consistently getting better in quality, and "Monster Next Door" is on the upper end of the scale among fluffy Thai BLs from 2024.