I tried calling the API and it seems to work with the partial address too:
https://maps.googleapis.com/maps/api/geocode/json?address= Krong Siem Reap, Siem Reap Province, KH&key=
{
"results" : [
{
"address_components" : [
{
"long_name" : "Krong Siem Reap",
"short_name" : "Krong Siem Reap",
"types" : [ "locality", "political" ]
},
{
"long_name" : "Siem Reap Province",
"short_name" : "Siem Reap Province",
"types" : [ "administrative_area_level_1", "political" ]
},
{
"long_name" : "Cambodia",
"short_name" : "KH",
"types" : [ "country", "political" ]
}
],
"formatted_address" : "Krong Siem Reap, Cambodia",
"geometry" : {
"bounds" : {
"northeast" : {
"lat" : 13.4692631,
"lng" : 103.9917327
},
"southwest" : {
"lat" : 13.2114327,
"lng" : 103.7341763
}
},
"location" : {
"lat" : 13.3670968,
"lng" : 103.8448134
},
"location_type" : "APPROXIMATE",
"viewport" : {
"northeast" : {
"lat" : 13.4692631,
"lng" : 103.9917327
},
"southwest" : {
"lat" : 13.2162611,
"lng" : 103.7341763
}
}
},
"place_id" : "ChIJeaiRjJoWEDER-rvlPvmqQKk",
"types" : [ "locality", "political" ]
}
],
"status" : "OK"
}