I am just a run of the mill, average tourist and want to travel in Thailand for about 6 weeks.

As a holder of a USA passport, I know I can get a "visa on arrival" good for a 30 day stay.

What would be the best/easiest option to get an extension for an additional 15 days or 2 weeks + or-?

How soon can one apply for this extension? I ask this because I know I will be staying beyond 30 days when I arrive.

I thought I read someplace that to get an extension of 15 days, there had to be good reason. Is spending money in Thailand as a tourist a "good" reason?

On previous tourist trips to Thailand, I have done that "visa run" thing to Cambodia to get another 30 days.

Is there an easier way?

I am just a run of the mill, average tourist and want to travel in Thailand for about 6 weeks.

As a holder of a USA passport, I know I can get a "visa on arrival" good for a 30 day stay.

What would be the best/easiest option to get an extension for an additional 15 days or 2 weeks + or-?

How soon can one apply for this extension? I ask this because I know I will be staying beyond 30 days when I arrive.

I thought I read someplace that to get an extension of 15 days, there had to be good reason. Is spending money in Thailand as a tourist a "good" reason?

On previous tourist trips to Thailand, I have done that "visa run" thing to Cambodia to get another 30 days.

Is there an easier way?

Probably better to just go ahead and apply for a tourist visa. Should be good for 60 days, with a possible 30 day extension. That way you wouldn't have to leave the country if you didn't want to.

You would not receive more than a 7 day extension of stay - they days of 15 plus extensions are gone.

You may not get on the aircraft without a visa if you do not have exit tickets within the 30 days and this may again be checked at Immigration.

As said - get a tourist visa if you plan to be here longer than 30 days.