So it turns out after some time on the phone with a JAL rep, that the REP->BKK, BKK->USM, USM->REP routing is legal for 8k miles. It wouldn't make sense to try and route from BKK->REP to same miles anyway, because they count the mileage of the surface sector in the calculation, putting it over 1000 miles anyway.

Even the CSR I talked to had to call another department to verify that this was indeed a legal routing, but he confirmed it was.

I'm going to transfer my SPG points. Here's hoping for a fast transfer.