This may bore you but please read.
I'm glad that your friend is at least an "electrician". Mind you, I spent 3 years in the Australian Navy (as an electrician) & 2 years in the Royal Australian Air Force (as a Radio Technician) & in neither of these sojourns, I learnt anything about "fault current". I did all of my "real" learning as a switchboard design engineer in civvy street (almost 10 years).
By the sounds of things (as you describe), your friend used a HRC (High Rupturing Capacity) fuse, which is nothing like a normal fuse. This kind of fuse has the unique ability to limit "fault current". You can easily tell an HRC fuse from any other as it has "HRC" written on it.
Running a cable in parallel with your main supply cables means that these cables must be able to safely withstand the "prospective fault current" of the supply. If the fuse is placed at the "load" side of the supply (the house end), the cables must therefore be able to tolerate this fault current. If the fuse is placed at the "line" side of the supply (the pole end), the cable will only need to tolerate the fault current that is limited by the fuse. There is a distinct difference between these 2 situations.
What I'm trying to say is that if your friend placed the fuse at the house end of the cable, VERY BAD!!! This fuse MUST be placed at the "beginning" of this cable to be of any use. Again, this MUST be an HRC fuse.
What is "Prospective Fault Current?"
It is the maximum amount of current that can be delivered by a supply under short circuit conditions. Consider a standard 150kVA 3 phase 380 volt transformer (normal for domestic supplies in Thailand & Australia). The impedance of these transformers is usually about 4-6%. By calculation & using the worst case value (4%), the prospective fault current at the transformer terminals is about 6000 Amps. This means that if a short circuit happens very close to the supply transformer, 6000 Amps will flow in the short circuit. Between your house & the transformer, you have lots of cable. The length of this cable will reduce this amount of current under these conditions. So, if you get a short circuit in your house & you do not have circuit breakers/fuses that are capable of safely disconnecting this fault, you will experience an explosion.
Since the DR uses the American system of wiring (yuk!), it's quite possible that all prospective fault currents for domestic residences, will be limited to less than 5000 Amps. In any case, this fault current MUST be considered when selecting circuit breakers etc.
Even though all of this may seem complicated (this is why "electrical" people are paid to figure this out), it must be realised that this old & unamazing thing called Fault Current is much more important than anything else, since it can destroy switchboards, homes etc in a matter of seconds.
Unless you know EXACTLY what you are doing with electricity, don't meddle with it.