The "time frames" are NOT called "Permission To Stay". What you have is a VISA. That is why you can change your Tourist Visa to a Non Immigrant Visa at the Immigration Office. Every document you need in Thailand like a Thai drivers license, a Yellow Book, a Pink ID-card, a Thai bank account, Resident Permit, buy a car/motorbike in your own name and proof of residence from the Immigration Office is based on a Non Immigrant Visa. Why is this so difficult to understand?