Spoiler alert!
When Ki-jeong frames the driver by leaving her underwear under the back seat, she does so without him noticing. If she can do this with such ease, it suggests she could more easlily make money as a stripper or karaoke hostess (which, lets face it, is probably the job a woman in her situation would have).

In a later scene, the Kims are eating in a canteen for what looks like taxi drivers and chauffeurs. If the father already has talent for driving, why isn’t he already earning money doing so? Not to mention the ease with which the Parks dismiss their former driver. If they valued him at all they would have confronted him about what happened..
When the former housekeeper returns, she finds the family behaving extremely innapropriately., getting drunk on expensive whisky and throwing snacks around. Yet she carries on as though this is normal.
Guen-sye, the husband under the cellar. Where to start with this one? The explanation for his hiding there is that there was an underground bunker built by the previous owners of the house. When her husband borrowed money from loan sharks, she sent him down here, obviously caring for him whilst she worked as a housekeeper. If this was before the present owners moved in, it would mean that he has lived there longer than 17 years (!) by which point, wouldn’t the sharks have given up chasing him? Then again, Pieta……https://en.wikipedia.org/wiki/Piet%C3%A0_(film)

The kid’s birthday party. Something strange about this; there don’t seem to be any kids here. Instead, there’s a woman singing o mio babbino caro, and a huge fire in the middle, not to mention an axe.

The killings. This scene was so badly shot that its actually difficult to see what happens. But lets see: Ki-jeong comes with a cake, which she smashes into Geun-sye, but after he has lunged at her with a knife, fatally stabbing her. This is in full view of the guests, who seem not to notice a deranged man with blood seeping from his forehead carrying a knife. Just before this, her brother is bludgeoned twice with a rock, seems to be out cold (but later makes a miraculous recovery). Someone kills Geun-sye with a barbecue skewer, the boy faints, and Ki-jeong dies. All of this could have been done better, but in a further bit of unlikeliness, the father stabs Mr park with a knife, killing him.
What do the Kims do with their money? Working at the Parks should have brought then some material benefits. strangely, despite all working good jobs, they continue to live in the tiny, semi-derelict flat under the ground.
Right at the end, we see Ki-teok writing a letter to his father (who uses morse-code signalling to send messages to his son). Except there is no way of Ki-teok getting the letter to his father. But wait. Immediately after killing Mr Park, Chung-sook can be seen running to the side of the house, down into the basement. In other words, it can be reached from the outside, which means the son could quite easily post messages directly to the father, give him food, even help him break out.
Whilst Mr and Mrs Park wait for their son to come out of the tepee, they make love on the sofa. As he starts to caress her breasts, she instructs him to move in clockwise direction. It’s clearly done for laughs, but it’s not really obvious why she would gain more pleasure from this.
On my first viewing, I felt that the Parks were parasitic of the Kims. When I watched it again, it was the other way round. I’m not sure the film is such a strong statement of class ( as has been claimed). The film highlights the social divide in South Korea, without really telling us anything interesting about it. Not to mention, the Kims hurt each other, displace hard-working people and are responsible for the murder of an innocent man.
All this means that I still enjoyed watching the film, I’m jsut surprised that the flaws seem to have gone unrecognised. The recent Japanese film Shoplifters looks at a family who struggle in poverty but act in a more human and believable way.