In my village on the outskirts of Bangkok there was a power cut about 15 mins ago and I heard a bang not far off so I guess a transformer somewhere has blown or something, anyway the power instantly came back on but it seems to be very weak or something for example the air works but not at full strength, fans spin slowly and the fridge appears to be off but the light inside is working but very dim.

Ive never seen anything like this before, whats going on?

Sounds like a brown out (low voltage) to me. You might not want to turn on anything expensive until the voltage returns to normal...

Most likely one fuse of the 3 phase transformer has blown (not the one you are on) so your power has been reduced to about 160v which will power most lights and fans will run slow. You should unplug refrigerators until full power is restored (can use the fan to check for that - likely they will kill all power for a minute and then full power will come back).

Brown Outs are hugely common in Thailand. PEA seems to in general have a problem keeping the voltage steady even without any catastrophic event.

You may well find any transformers or constantly running motors emitting a loud hum as the voltage dips.

Generally modern appliances such as refrigerators will deal with it, but overall it's not good.

But this being Thailand, all par for the course.

Buy a UPS to run any sensitive computer products you have, generally their software will also give you a pretty telltale insight into voltage stability...it feeds the inner geek in all of us

Pay attention to the advice about shutting down anything expensive or sensitive. Last week in Pranburi we had a massive storm cause one line of the three phase power to go down and cause the dreaded brown out.

In the morning, the Wifi router, network cable switch and power supply inside the computer were all fried.