What are the current travel requirements for unvaccinated travelers flying from Thailand to the US and back?

As long as you are just transiting, and not going through immigration, and getting your luggage, you will be just fine. The issue would be with you being allowed on the first plane. That point is the original point of departure, and as long as they allow you to board, all the rest of your transit points will to.

Your negative covid test has to be taken one calendar day before not 24 hours

Entry back to Thailand is currently insurance, pass and a PCR 72 Hours prior. Could change depending on when you plan on returning. If transiting through Canada you are exempt from any requirements. These are from travel.gc.ca.

Transiting passengers who are only flying through Canada to reach another country

For requirements, see Transit to another country by air.

Exempt from pre-entry test

Exempt from arrival test

Exempt from Day-8 test

Exempt from quarantine

Transit to another country by air

You may be permitted to transit through Canada to reach another country. You must make your travel arrangements well in advance if you are transiting through Canada.

While travelling

You must follow all flight requirements and comply with any guidelines provided by the Airport Authority.

Boarding flights to and within Canada

During your connection at the Canadian airport

You must remain in the secure transit area to complete your connection. This means that you won’t be allowed to collect your baggage, or check-in for your next flight anywhere but at your scheduled gate of departure.

You’re exempt from testing and quarantine requirements, as long as you remain in the secure transit area to complete your connection within 24 hours.

If you want to leave the secure transit area due to a flight cancellation or delay, you must be eligible to enter Canada.

Doubt they will let you on the plane if there're any issues so if you get to board your good to go

Should have had your 2 jabs makes traveling easier lol 😆