It looks like the Thai "Type-O" plugs have the same specs as Israeli "Type H", and the plug looks similar, but "upside-down":

Type H:
enter image description here

Type O:
enter image description here

Can you actually plug one kind into the other?


No, they aren't.

From reading Power plug & outlet Type H and Power plug & outlet Type O it appears that they are not compatible. The latter link explicitly says

Although they look similar, type O plugs are not interchangeable with the Israeli type H

Also from Israel SI32 (Type H) it says

The pre-1989 system has three flat pins in a Y-shape, with line and neutral 19 mm (0.75 in) apart. The plug is rated at 16 A. In 1989 the standard was revised, with three round 4.5 mm (0.177 in) pins in the same locations

And Thai 3 pin plug TIS 166-2549 says

The plug has two round power pins 4.8 mm in diameter and 19 mm in length, insulated for 10 mm and spaced 19 mm apart, with an earthing pin of the same diameter and 21.4 mm in length, located 11.89 mm from the line connecting the two power pins

There is a difference in the pin diameters. Depending on which way you are trying to plug things in you could potentially either jam things in or have a loose connection. There may be enough mechanical play to do this, but I would not recommend doing it.

And I love this quote from the World Standards website (above)

Type H plugs are among the most dangerous ones in the world: the prongs are not insulated (i.e. the pin shanks do not have a black covering towards the plug body like type C, G, I, L or N plugs), which means that if a type H plug is pulled halfway out, its prongs are still connected to the socket!

  • 1
    1. A .3mm diameter difference is quite possibly within the tolerance of a socket's plastic... how sure are you that it won't fit? 2. I don't understand your latter quote. Even with the covering toward the black body (like in C plugs) - if you pull a plug half-way out, the part that's still connected to the socket is the exposed end. – einpoklum Feb 17 '19 at 16:50
  • @einpoklum It's not a brilliantly written statement. The part that isn't stated is that the live pins then extend out of the socket for you to accidentally bridge with a dropped metal object (or your fingers). – origimbo Feb 17 '19 at 16:57
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    @einpoklum If you plug the smaller diameter pin into the larger diameter hole you risk causing arcing in the socket - especially in an older socket that is already worn. That is a fire hazard. Plugging the larger into the smaller could damage the socket to the point that it causes arcing for the expected pin size. So yes, you can use a hammer to make the plug fit, but that doesn't mean you should – Peter M Feb 17 '19 at 16:59
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    @PeterM: 1. Of course there's a theoretical hazard, but: 2. We're talking about a .3mm difference here. The metal on the other side will probably accept either of them fine, because it has to apply some counter-pressure anyway; the plastic would likely also budge. The point is that 3. You're speculating based on the official description of the socket types, not empirical data. – einpoklum Feb 17 '19 at 17:45
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    I frequently put plug type J (Swiss, 4.0 mm) into type E (French, 4.8 mm), which works without any issues (the plug will tilt down due to gravity, which gives a good-enough connection). The opposite however is impossible due to the different diameters. 0.8 mm is however significantly more than 0.3... – a20 Feb 17 '19 at 22:54

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