TL;DR Will I get taxed on a bunch of household stuff like a TV, mattress etc? How about a PC in a suitcase?

Pre-pandemic I lived in Vietnam, I left a bunch of stuff there and came back to Australia for what was going to be a short stay but ended up being stuck here a while. Now I'm planning on moving to Cambodia but I have most of my household stuff in Vietnam and a PC in Australia. Ideally I'd like to put my PC in a suitcase in parts, fly to Cambodia, find a rental, go to VN, pack my stuff in a truck and meet them back in Cambodia, or cross the border with them if need be. I can't find good info on this online, it varies from lists of banned imports that seem to cover practically everything to claims of a flat 10%, and the reality on the ground might well be that nobody at land borders cares, since they seem pretty casual there in general. Anyone done it or have some expertise on this? Thanks.

How much is the stuff in Vietnam really worth and is there anything particularly special amongst it? Most rental apartments here are fully furnished, you might be better off selling it. Alternatively, go to one of the bus companies (try the ones on Sihanouk Blvd near the Olympic traffic lights) and ask them what you could bring/send with them that they can arrange to come across the border without any issues. Most of the buses on that route are licensed to do the whole trip and they rarely seem to have to offload the luggage.
Bringing the PC with you should be OK if you are travelling with it.

1)Make a detailed list of all goods that you intend to move at full purchasing prices. Contact a handful of international shipping agents and ask about prices for paperwork and taxes to be paid.

2)you show up at the border and try to bribe your way through. May take some time.

3)Get rid of everything that you can easily rebuy at destination.

This situation is a bit different from yours.

About 6 years ago, a friend of mine moved from Thailand to Vietnam overland via Cambodia. He's a pack-rat so he had about 40 boxes of stuff, a flat screen tv, couple mountain bikes, at least one PC, etc. in a lorry.

I checked with him and he said there were no taxes or hassles at the Thai-Cambo border when he arrived around 4 pm. They asked where he was going, and he said "Vietnam" and that was the end of it.

Maybe the fact that he was continuing onward was a factor but they weren't too bothered about his stuff.