What are the steps for applying for a Non-O visa for a spouse while applying for a Non-B work visa in Thailand?

SOME consulates make the primary visa holder (which is YOU) get their visa (the Non-B) first and after that you apply for the "trailing spouse" Non-O using your visa and documentation as proof of why the trailing spouse qualifies for the Non-O visa.

You can try applying for both at the same time, upload the marriage certificate, the documentation from your company you used to apply for the Non-B, make sure you have a letter from the company saying it's okay for your spouse to get a Non-O visa off your Non-B <- a company is NOT obligated to provide this and some companies give no trailing spouse/family visa support documentation at all

They'll either approve it OR message you that you have to upload your approved visa, OR they'll reject his application <- those are about the only ways it could go

You are correct for your spouse Non-O you want to select the choice

𝗧𝗼 𝘀𝘁𝗮𝘆 𝘄𝗶𝘁𝗵𝗶 𝗻𝗼𝗻-𝗧𝗵𝗮𝗶 𝗳𝗮𝗺𝗶𝗹𝘆 𝗿𝗲𝘀𝗶𝗱𝗶𝗻𝗴 𝗶𝗻 𝗧𝗵𝗮𝗶𝗹𝗮𝗻𝗱 (𝗺𝗼𝗿𝗲 𝘁𝗵𝗮𝗻 𝟲𝟬 𝗱𝗮𝘆𝘀)