GTM Topology configuration

So if you have multiple matches, the highest weight wins. Also, if you have multiple records match, but the destination is not referenced in the wideIP, then the record is ineligible. This should mitigate your concern for future expansion of topology. So for this instance, you'll need IP source for Korat & Colorado. You'd place a slightly higher weight on the records for Korat & Colorado, then you could build a Continent is Asia record to send all Asia requests to Singapore, then a Continent is not Asia to send all other requests to Oklahoma.