Can I change my job in Thailand while on a 90-day Non-B visa tied to my employer?

As todd mentioned you need the new job first it makes life easier. If you leave the current job your employer will cancel your work permit you visa is tried to that work permit so in essence you visa is also cancelled. So you will have to leave and come back on visa exempt. You then find a new job get your paperwork from employer go out apply at thai embassy for non B 90 day go back and your new employer applies locally for the visa extension and work permit

If you're on the initial 90 day Non-B that was gotten with support documentation from your employer (meaning you haven't gotten an extension on it) you can't switch jobs/employers on it.

You can stay until the 90 days runs out and then go get a new Non-B or come back in free stamp and apply for a Non-B at your immigration office with documentation from your new employer

Where as IF you have already gotten a year extension on your initial Non-B at the immigration office you CAN change employers inside the country.

You would get documentation from your current employer (the one you're leaving) and the new employer (the one you're going to work for). You'd go to the immigration office, cancel the existing extension you're on AND at the same time you'd apply for a new extension with documentation from the new employer for 1900baht.

It can be done, but it takes coordinating between both the old and new employer to do it.