yes I have year extension of my visa and multiply entry stamp. I am happy to travel with both passports. I just do not want to be stopped by immigration saying that I can not do that.
For tourist visa defenitely. If they do not ask and you have the documents. Nothing will happen. If they ask and you have no documents, you will be in a trouble. Simple is tbst
Thailand is a country where anything is possible. Therefore my suggestion is that you should always be ready to show officials sufficient amount of money. Never assume that they will not ask. That is what put people in difficult situation.