I have a US J-1 visa that will expire on July 20th. I want to go to Mexico before I go back to my country on July 17th for 3 weeks. Will I be able to enter Mexico?
If your Thai passport and the US J-1 visa in your passport both remain valid at the time you travel to Mexico, you will be able enter Mexico for tourism and vacation, then fly back to Thailand without reentering the US.
Source: IATA Travel Centre.