Can I enter Thailand on a 30-day visa exemption while waiting for my e-visa approval?

Hi everyone, my e-visa application for a Tourist Visa (Multiple Entry) may not be approved on time when I'm leaving... If this will be the case, is it possible to enter Thailand on my FIRST ENTRY via 30 days visa exemption (since my visa is still not approved) If the visa would get approved while I'm in Thailand already, could I just leave to a NEIGHBORING country for a few days and than re-enter Thailand again with the TR Multiple Entry visa from e.g. Singapur? I'm not sure if this is working for the Multiple Entry Visa since the req. is that you have to be in your home country while applying for that visa (what I was during application) Thanks for your help already!