A site called Travelfish.org are to be congratulated. Whilst all the other sites I found slavishly repeated that Thailand’s voltage is 220V, only Travelfish told the TRUTH: it is ANYWHERE BETWEEN 220V – and 240V.
In Bangkok it is all OVER the place, whilst here in THIS town, it sits at around 237-8V. Nearly 10% TOO HIGH.
Luckily, most appliances these days have Switch-Mode Power-Supply Units that can tolerate ANY voltage between 80V/180V and 260V, but if you have an appliance that is voltage-CONSCIOUS – WATCH OUT!
I blew out two sauna heating elements after a mere three hours EACH – then I metered the voltage – and subsequently built a circuit to DROP it by 20V. Now, my elements last about three YEARS.
And this is not unusual, particularly in less-developed countries, where the electricity companies figure they have had a good day if they can just MAINTAIN power for it.
Even in the developed countries, voltage drops during peak time, rising in between.
Although the funniest part comes with maintaining the timebase (50 Hz in most countries – 60, Stateside). You might imagine a few Hz more or less would make no difference – but there, you would be WRONG.
Synchronous motors, TV transmission equipment – and mains-operated clocks – DEPEND on that number being RIGHT. So in developed countries, generators are SPED UP overnight, until the count is right – which is why your mains clock may be up to half a minute OUT at various times during the day – but stays that way for YEARS.
Of course, companies with equipment that RELIES on a steady voltage often have regulators built in – but if their consumption is high, those regulators’ prices are too.
Most people take it for granted that 240, 220, 127 or 110V is 240, 220, 127 or 110V. But a quick test with a meter – which any Radio Shack or similar should have, at prices starting around a tenner ($16) – may well show you otherwise.
But do not overly concern yourself – as stated above, these days most appliances have sophisticated PSUs that will level out even the most amateurish power company’s supply.
However, even THEY cannot defeat SOME of the surges and on/offs that those companies deliver.
In ten years here, the local one has DONE FOR the afore-mentioned two sauna elements, a TV, another TV’s audio chip – thank gawd electrical appliances are CHEAP these days…