Baxter Pondsmyth Yep. If you want to apply via HCMC you have to be physically in a location served by that consulate, not just Vietnam as the locations are divided amongst the 2 consulates there. Then you need to stay there until you have the visa. Alternatively you could possibly apply using the consulate for where you currently are and wait there for the visa
Basically because Thai consulates treat applications traditionally even though all communication and document transfer is electronic. They all require you to apply online from the physical location served by the consulate you want to apply through and they expect you to remain there until the process completes
as you can see above it varies by immigration office but you are going to have to show you met the requirements of your previous extension as well as the upcoming extension. For me that means 12 months bank statements, a guarantee letter from my bank and my bank book updated on the day I go to immigration
there's no problem with withdrawing the 10k as long as it doesn't put you under 800k, which has to be in your account for 2 months (3 in some places) before you apply for the extension, it has to stay there for 3 months after and can't go below 400k at any point