Why does everyone in Laos answer the phone, “Hello, Sabaidee”, even when they don’t speak English?

It’s not as if all other Asians use the “hello” greeting when answering the phone. The Japanese say “Mushi Mushi”, Hongkers say “Wei?” and the Koreans, well I don’t know what they saw but I’d speculate that it isn’t hello.

I’d be interested to hear why people think “Hello” has become part of the common phone answering greeting in Laos, or at least in Vientiane. What do the Thai say? What do the Vietnamnese and Cambodias say?