Can I enter Thailand visa exempt if my Non-Immigrant B Visa isn't approved before departure?

I’m wondering if anyone would have any knowledge about the following.

I have a flight departing from the United States for Thailand in early August. I am waiting to receive one required document before I submit my application. Once I receive the document, I will be submitting my Non-Immigrant B Visa application online through the Thai E-Visa website.

If my Non-Immigrant B Visa isn’t approved by the time I depart from the United States, is it possible for me to enter Thailand Visa Exempt while I wait for my Visa application to finish processing? If this is possible and if while I’m in Thailand my application on the Thai E-Visa website is approved, how would I go about activating my Non-Immigrant B Visa since I’d already be in Thailand.