Is it possible and have 2 visum to two different countries in passports, as O visa in Thailand and O visas to Korea ?

Of course. Why would you think otherwise?

EDIT Do note that some countries won't give you a visa if there is a visa from a particular other country already in the passport, but these are few and do not include the countries in your example.

is there such a thing as an O visa for Korea ?

is there such a thing as an O visa for Korea ?

I think that was intended to be an example not stating there is one.

Yes you can have valid visas to more than one country in your passport.

An example would be if a person has a valid Thai multiple entry non immigrant visa and crosses the border to Laos or Cambodia to get a new entry they would have two visas in their passport at the same time.

I think If I went back to one of my old passports I would find 3 in one of them.