Oei is commonly found in Indonesia. It is the Chinese name Huang (黄), pronounced in Hokkian and written using Dutch spelling.
There was a period in Indonesia when the Chinese were pressured to Indonesianize their Chinese names. Examples of the evolution of OEI:
Darwis, Wienathan, Wibowo, Widiatmo, Wijaya, Widjaja, Winata, Widagdo, Widodo, Winoto, Willy, Willys, Wiryo, Wirya, Wongkar, Wiryanto, Wiraatmadja, Winarto, Witoelar, Winardi, Wibisono, Wiryono, Wiranata, Wiryanto, Wiyono, Wijono, Wuisan, Wisanto, Wijanarko, Wijonarko, Windra, Jingga, Ngadimin, Ngadiman