I thought you could only get a 30-day visa that's valid for a 6 month period, and spend a maximum of 90 days in Thailand within than 6 month period if you count re-entry. Going for visa runs very four weeks can't be that fun.
I'm British, so maybe its easier. You can get a 3 month tourist visa, with a 3 month pending extension from the London embassy.
Failing that you can do a 'border run'. I quite like being near Chiang Mai or Pai. From there its about a 3/4 hour drive up to Burhma. I did it with a mate of mine for a day out.
If you're outside of Thailand, you can get a 60 day visa for about $30, and that can be extended a further 30 days once inside Thailand for another fee (I never did this, but I think it's around another $30.) The consulates in countries around Thailand are aware of people entering, leaving and getting a new visa, then re-entering. Certain consulates will almost always give the visa, some will deny if they see repeat visits - it really depends on the guy looking at the paperwork at the time sometimes.
For example, when I was there last year, the consulate in Penang, Malaysia was known to give back to back 60 day visas as long as you never did the 30 day extension. But they wouldn't give the multiple entry visas that basically give you the 60 days + 30 days extension each time you enter the country for 2-3 entries.
However, everything can be bought there.... Everything.
You can get your 90 day without too much hassle, I would recommend this lawyer firm, as I have used their Chiang Mai branch and found them good, however they are a big firm, so YMMV. http://canada.siam-legal.com/90-Day-Thailand-Visa-for-Canadi...
I would have thought that the worst case would be a 5 day gap between two of these, obviously, check with the lawyer.
If you want to spend 5 days in a nearby nation you are spoilt for choice. Myself I like Vietnam, the food is really good, friendly people, stunning, stunning scenary.