I'm a citizen of two different Schengen countries (Sweden/Finland) and i have exclusively used my swedish passport to travel in/out of Thailand. What i'm basicly asking is if the immigration will give me a "hard time" travelling in with my finnish passport in the future (from Europe)? I assume the computer system is smart enough to notify to the imigration officer about my previous entries to Thailand on my swedish passport so they would see my picture and swedish passport and now i was using a finnish passport...

You can use as many passports you have, there is nothing illegal in doing that and certainly you're not the only one doing so.

OP

Why do you believe this may be an issue ?

I think it's unlikely the computer will make any association between you on the Finnish passport vs Sweden one. Why would the computer assume it's the same person? Different passport, different number, etc.

I think it's unlikely the computer will make any association between you on the Finnish passport vs Sweden one. Why would the computer assume it's the same person? Different passport, different number, etc.

I think that immigration's computer is a lot smarter than you think.

They will do a name and date of birth search which will show the complete history a person has. When a passport is used for the first time for entry it will do that automatically.

Makes sense. I know you have to use the same passport on exit that you entered with.

Done that myself, used my Swedish passport when coming here as a tourist.

Using my Finnish passport when living here as the Finnish Embassy in BKK have better service that the Swedish.