Making telephone call to Thailand from overseas

[connda]

I'm confused.

In Thailand when I what to call my wife, I dial 089+<her number>.

Outside of Thailand, I dial 66+89+<her number>

Why is the zero '0' not used in International calls, but is used domestically?

[N47HAN]

Same all over the world.

Not sure why , maybe an esteemed member can put you out of this serious dilemma you face , must be tearing you apart not knowing

[Aachen]

Except the USA, where everything is different, the 0 shows national calls to be outside your city. Mobile is always outside (technically). When you call from abroad it is clear by the origin, that there is no in or out, once you are in Thailand by +66 ... In German the 0 is called Verkehrsausscheidungskennziffer ...