GTM Topology configuration

You could do topology at the pool level, separating singapore and korat into a pool and oklahoma/colorado into a pool. Then you could further do topology within the singapore/korat pool, and use another method for the US (least conn / rr / vs capacity, etc). It really boils down to what your business rules are. If you can narrow down the business rules it would help. For example, should all users outside singapore go to US, or should all asia requests hit korat or singapore. Except for singapore, does it matter which DC the requests go to? For all other world users, should they go to colorado, oklahoma, or both?