I am coming to Thailand 2 times later this year. Once will be less than a month and 1 time will be longer than a month.  Both trips will be completed within 4 months.  I have always traveled on a 30 day tourist visa upon entry.  As I will be in LOS for longer than a month on the second trip, I need to know what  visa should I apply for to enable me to travel on boths trips.

    If it helps, I can mention that I am traveling with my Thai wife and child from America in September and returning to the USA in 3 weeks.  They will stay there. (My son has a single entry visa)  I will return in November and we all will travel home to the US in December.  Thanks

You'll need a double entry tourist visa. Even though your first stay is less than 30 days, you'll find that you cannot reserve  a visa for future use.

The previous poster is correct but seeing your first visit will be less than 30 days you can apply for visa on arrival. When back in US you can then apply for single entry for your second visit which is more than 30 days. Either way you will be making an application for visa in the US. Might be quicker than getting visa on arrival.