Ask agent at origin if the 2 airlines in question have an interline baggage agreement, if they do, show her your confirmed itinerary and she should be able to tag them thru. Good luck..
talk about other countries getting the same 90 days exempt as well, but those countries must also open up for Thai citizens as well, sadly most westernized countries are still not doing that, it's virtually "impossible" for thai's to come to USA, especially if you are a single woman,,,,time will tell!