I was going to ChaengWattana before I move to nontaburi. At there if you go early can finish quickly but after move to nontaburi I went to nontaburi immigration. Like you said doesn't matter at what time you been there. All day need to wait. School manager probably will not understand this and also even if you want to go chaeng wattana they will send you to nontaburi anyway.
The ask:thailand community, consisting of multiple Q/A groups with over 100,000 members, powers this platform. It is not an official government resource. Our members actively contribute to this resource, and while we strive for accuracy, we cannot guarantee its complete reliability. Assistance to travelers is provided as a community service.