If the load is still intact, and there is a L-E (frame) fault, then it helps to separate the current flows which we'll assume for now are independent.
1) The normal load current. For this, the currents in L&N will balance and not trip the RCD.
2) The current due to the fault. This flows from whatever has contacted the frame (we'll assume the L supply) and down to the protective earth connection. The size of this depends on the circuit impedance. If the frame is perfectly isolated from ground, nothing will flow. If it's well connected then a large current will flow and the supply over-current protection (fuse or circuit breaker) will blow/trip. In between these two extremes, some current will flow and if it's large enough then either the RCD or overcurrent protection (or both) will trip.
In a properly wired UK system, any fault current will NOT flow back through the neutral connection - it's expressly forbidden to have the circuit neutral share a connection with the earth connection (at least, once past the supplier's service head and you'll find some threads here and over in the DIY-Not forums about "lost PEN" faults (loss of the protective earth and neutral, PEN, conductor) on the supplier side. Since the earth connection does not go through the imbalance sensing coil of the RCD, any current flowing in the circuit's earth conductor will not balance that in the live conductor and (if large enough) will trip the RCD.
Now, you are not in the UK, and i gather some countries have what we might describe as "interesting" ideas regarding electrical safety. As you have no earth wiring, it sounds like Cambodia is one of them. If exposed conductive parts are "earthed" by connecting them to the supply neutral (which we'll assume is earthed, making it a TN-C system) then things do get more interesting.
If it's as simple as having a 2-pin plug & socket, and the appliance case is connected to neutral, then a L-case (frame) fault will not trip an RCD - there will be a current from L, through the case, and back out of the neutral wire. Since (again, apply Kirchoff's current law) "what goes in must come out", L & N currents will still balance and the RCD will not trip - depending on the nature of the fault, the overcurrent protection may trip, or the case may become live to some extent. Only if someone touches the case while also touching something "earthy" will a current to earth flow - and that should trip the RCD. On that basis, having an RCD will be safer than not having one as long as you don't then lower your guard because you consciously or subconsciously think "it's safe now I've got an RCD".
Possibly the worst case fault in this situation would be a broken neutral somewhere together with another fault. That could make the case of every appliance go live even when they are switched off ! That's the situation I mentioned above about loss of the PEN on the supplier's side - there's scope for the "earth" connection in a property to become live, not normally a problem inside as we have equipotential bonding, but a problem once we export that equipotential zone outside (such as to a metal tap or an EV on charge).
As to whether you can usefully do much about it, that depends on local custom, local regulations, and your personal situation. For example, if you are in a position to create your own earth electrode (a.k.a. earth rod), then you could potentially convert to a TT system in which case you would need RCDs to provide safety, but they would probably protect better than you have now.
Try this page which will probably help, or
this page.
