I happened to me as well. I applied for a one year visa, showed the required bank account with money they wanted to see and got a single entry non imm O. Got 90 days on entry
Chiang Mai is strict, they advise you to come 2 weeks in advance (for your Thai family extension). You will get 30 days under consideration. If you come more early your"under consideration" period will be longer. Last time I got 7 weeks...