Museum of Plugs and Sockets logo, small TIS 166-2549
Thai standard plugs and sockets
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TIS 166-2549* plugs and sockets have developed in Thailand in 2006. Sockets accept both round pin plugs with a 19 mm spacing between L and N pins, and US straight blade NEMA configuration 1-15 and earthed 5-15 plugs (respectively type A and B).
To accommodate Thai earthed round pin plugs a new (type O) plug type has been introduced that has the same earth pin offset as US earthed plugs (= 11.9 mm).

Electrical network in Thailand operates at 230 Volt, 50 Hz.
Finally compatibility with straight blade plugs is to be phased out.

* Thai solar calender year 2549 corresponds to 2006 according to the Gregorian calender.

Type O


Thai socket for type not earthed plugs Type A, B, O dual earthed socket
TIS 166-2549 plug Sokawa 2-pin plug Thai Europlug-style appliance cord plug

Thai Schuko adapter Thai Schuko adapter Thai Schuko adapter wiith Schuko plug Thai Schuko adapter, detail

1 Classic not earthed dual socket for plugs with two round pins 19 mm apart, and US NEMA 1-15 straight blade plugs.
Slots for straight blade plugs have unequal width: left = 7 mm, right = 8.5 mm (comparable to US specifications).
Rating is not indicated. Thai Nation (see top of socket) is probably not the manufacturer's name.
2 Modern Thai socket with earth connection, rated at 16A - 250V. Socket has switches; convenient but not compulsory.
The earthed outlets accept:
(1)  TIS 166-2549 2- and 3-pin round pin plugs (see images 3, 4 and 5);
(2)  US NEMA 1-15 ungrounded straight blade plugs and the 5-15 version with earth pin (but note Thai 230V mains);
(3)  CEE 7/16 Europlugs. The round pins of Schuko plugs will fit also, but an earth connection is lacking (see nos 6 - 9).

Thailand, similar earthed sockets can be found also in Cambodia, Laos and Vietnam.
Manufacturers: Schneider Electric (German company, socket made in China)   {MH}

As of 2008 it is a legal requirement to fit the newly developed Thai standard TIS166-2549 plug on imported appliances that  have a cord with Schuko plug. TIS166-2549 10A, 250V plugs fit in socket shown in image no. 2.
L and N pins have insulated sleeves. Pin diameter is 4.8 mm. Earth pin is 2 mm longer than L and N pins. Earth pin offset is 11.9 mm.
Plug has a TWF mark which stands for Thick Wide Flange (indicated by green arrow).
Manufacturer: Yunhuan Electric, Yuyao City, China. {DC} 

TIS 166-2549 plugs are molded on an extension cord, but from 2022 (?) also rewirable plugs should be
for sale.  {DC}
4 Rewirable 2-pin plug rated at 16A - 250V. Pin diameter: 4.8  mm; pin spacing: 19 mm. Pins have insulated sleeves.
Manufacturer: SOKAWA, Thai company active in plastic and metal moulding and retail of electrical accessories.   {MH}
5 Europlug-like TIS 166-2549 appliance cord plug, rated at 6A - 250V. Pins have insulated sleeves. Pin diameter: 4.8; pin spacing: 19 mm. Note that because of the 4.8 mm thick pins, it can be difficult to insert the Thai plug into an Europlug specific socket or connector plug, designed for 4.0 mm pins.  
Manufacturer: DATA Trusted Power, Bangtoei4, Sampran Area, Thailand.   {MH}
6 - 9
For already existing appliances equipped with a Schuko plug, an adapter can be used.
The Thai Schuko adapter provides for an additional earth pin (see no. 6) which is connected to one of the earth clips of a Schuko plug (see nos. 7 and 9). The combination of two Schuko pins (N and L) and the earth pin of the adapter (see no. 8) will fit correctly in an earthed TIS 166-2549 socket (see no. 2).
Note that the adapter has disappeared from general hardware stores and it is not clear whether they are still available elsewhere (info given in 2016 by John Goodwin).


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