Type O is used exclusively in Thailand. The type O socket and plug, rated at 16 amps, are the official standard in Thailand. The plug system was designed in 2006, but its use is not widespread as yet. It is currently gradually being phased in. The standard is described in TIS 166-2549.
Type O consists of two power pins and an earth pin, which are round and have a 4.8 mm diameter. The power pins measure 19 mm in length, they have 10 mm long insulated sleeves and their centres are spaced 19 mm apart. The earth pin has a length of 21.4 mm. The centre-to-centre distance between the grounding pin and the middle of the imaginary line connecting the two power pins is 11.9 mm, which is exactly the same distance as in type B plugs. This is not a coincidence, since the hybrid version of this socket was originally designed to accommodate plug types A, B, C and O. In the long run, compatibility with American plugs is planned to be phased out, since the electrical network in Thailand operates at 230 V. Although they look similar, type O plugs are not interchangeable with the Israeli type H or the Danish type K power plugs.
Can somebody please enlighten me as to why on earth a country would develop a whole new kind of plug and socket system when there are several alternatives available? Standardizing on the international type N (or, for that matter, another safe and earthed plug system that is compatible with type C, such as F or E) is of course self-evident. As the Thai Government is going to phase out compatibility with plug types A and B anyway, why haven’t they adopted the type N standard, while at the same time allowing for a period of transition where hybrid B/N-receptacles as well as type N sockets may be installed? This is absolutely mind-boggling!