There are many reasons why you might want to travel to Thailand, and there are other reasons why you may wish to apply for a non-immigrant visa.
Tourist visa may be granted to short-term visitors who intend to stay in Thailand up to 60 days per trip, while Multiple Entry Visa (METV) is valid for 6 months with multiple entries. Tourist visas are good for short stay but not so good if you plan to live long-term.
There are strict rules for short and long-term foreign visitors in the Kingdom.
However, for long-term stay, things are much simpler if you are married to a Thai citizen, have a Thai parent, have a dependent who is Thai, if you are over fifty years old, or you work for an international company based in Thailand.