Entry and exit with different passports

[BKResort]

I hold 2 passports...One from the USA and other from Italy. Both valid. I am on a retirement extension with my US passport. Never used the Italian passport in Thailand.

Can I exit Thailand using my Italian passport?

[lopburi3]

No. You must use the passport of nationality you entered as to exit. If you want to make a switch you exit and then return using other passport (but remember at land crossings they will likely want to seen both exit/entry stamps in same passport.

[Seizetheday]

Why don't you try!!! The immigration officer might be a bit perplexed why there is not an entry stamp in the Italian passport though!!!

[Suradit69]

Why don't you try!!! The immigration officer might be a bit perplexed why there is not an entry stamp in the Italian passport though!!!

He wont be perplexed. He'll want to know how he could legally be in Thailand without any permission to stay stamped in his passport. If the o/p has a valid retirement extension that he wants to maintain, then he ought to have a re-entry permit in the same passport that the extension is in. If he wants to return using the other passport and nothing else, he'd just be given a visa exempt entry.