Okay, I hope we now all understand the visa doesn't "activate on arrival" :O The visa is VALID for 6 months from the date it's issued and you start losing time off it the second you get it. That's why
@Lance ******
said to get it as close to the time you're going to come here as you can. That way you don't burn the validity of the visa down not being here ;)
You get unlimited 60 day entries to thailand on the visa for it's validity and most people can wring close to 9 months of stay out of it (in 60 day increments and by extending the last entry by 30 days).