What kind of electricity sockets do they use in Thailand ? Answer: A hybrid system of European standard and American standard. That means that a plug from continental Europe (2 pins without grounding) and a standard American plug (2 pins without grounding) will work fine.
Due to the combination of the American standard and the European standard the holes have one flat side and one round side. This makes both types of plugs fit in the socket. This same system is used in other Asian countries like Laos, Vietnam and the Philippines.
In most western countries sockets with a ground connection are required by law for safety reasons. In Thailand however the ideas about safety are different. Also for electronic installations. Therefore it is completely normal to have ungrounded sockets (2 holes only). Sometimes you’ll find grounded sockets (3 holes) and ungrounded (2 holes) in one hotel room. Since chargers for mobile phones, tablets and photo cameras usually don’t use grounding (2 pins) it will always fit in Thai sockets.
As seen in the previous pictures; European plugs with a ground connection will fit in a Thai socket. However there is no way that the ground pin is connected. Your electronic devices will work fine but off course it is less safe.