Type C vs. Type O

Type C, the "Europlug," is the most widely accepted plug in the world by country count -- 2 round, slightly tapered pins, ungrounded, rated just 2.5A/250V. Its flexible pins give it a secure friction-fit in sockets built for several other, larger round-pin standards.

Type O is Thailand's standard, introduced in 2006 -- three round pins whose earth-pin offset happens to numerically match Type B's, letting Thailand's real-world hybrid sockets also accept American Type A/B and European Type C plugs. Pure single-standard Type O outlets barely exist in practice.