I have a few Thai/US citizen friends that are in Thailand on US passport and and living on extensions in Thailand. Is it possible to depart Thailand via land on US Passport (thereby cancelling stay or extension) ,and reenter on Thai passport. We tried this at Chong Mek but they would not stamp the US passport and allow them to reenter on temporary border pass issued in Thailand. I don't understand what the problem is but they said that they needed to get an entry visa on US passport for Laos and them when they returned they would be given 15 days. They do not what to enter on US Passport and asked if they could enter on Thai passport. No cannot do illegal. What gives here. Do we have to leave throught BKK and return at the airport? Technically you are doing the same thing at the border, only walking out and back.

Someone hopefully will explain better but I seem to remember that the only place you can change Passports is in the air.

You can not change passports at a land crossing as each country will be looking for the previous country stamps in your passport. Only air travel avoids that check (as many air destinations do not stamp passports).

there have been lengthy discussion and posts several months ago on the two passports issue.

it appears that a person with two pp could do the switching quite easily when traveling by air....

and several posters recounted their own successful switching at bkk airport, without any problem--embarking and disembarking as well....