I have 2 passports from 2 countries, USA and Mexico.

My US passport is due in 5 days, with a NO Visa and not time to get a new one before my NO visa expire.

My Mexican passport is OK but not Thai visa on it.

Can I leave Thailand walking out the border with the US passport and entry again with my Mexican passport?

If I can. What border is the best to do that?. I live in Phayao, close to Mae Sai (Burma) and Chiang Kong (Laos)....

Thank you for your advice.

Passport change can not normally be made at a land crossing as both countries will check for exit/entry stamps - best to make a flight somewhere and return - or get an emergency passport from US Consulate (immediate issue).

Edit: but not sure they would be happy to issue for forgetfulness rather than actual need for travel.

Passport change can not normally be made at a land crossing as both countries will check for exit/entry stamps - best to make a flight somewhere and return - or get an emergency passport from US Consulate (immediate issue).

Edit: but not sure they would be happy to issue for forgetfulness rather than actual need for travel.

In case I decide to fly..What passport I have to use to exit Thailand? Airports do not check entry stamps? Can exit with my Mexican passport? No stamps on it...and the US will be expired. Still confused about....

You must exit with the passport used for entry. You said your Mexico passport was OK but also said visa not in it? Did you mean your current entry visa or that there is no visa in it? Believe you will need a visa for entry using that passport. You also should exit before you passport expires - your stay can not be for beyond that date. Something is very strange.

You will need a visa to enter Thailand. Mexico citizens do not get visa exempt entries or visas on arrival.

You best option may be to get an emergency passport from the US embassy.