The fire happened at an odd place in the bus. Why nearly no one got out, is unknown at this moment. And the whole thing is most likely not the drivers fault. Why he ran away: no idea.
Non O Visa based on volunteering. Check your own countries eVisa system. And do not ask on FB ... use google. Basically every answer you got here is wrong or misleading.
Yes you are missing something. You can do border runs as long as you want. They "might" once ask you what you are doing ... then you just explain.
And as others pointed out: when they explain, you get a visa next time, and all is good.
The 2x per year leaving and coming back rule for land borders got dropped in June.
And coming from Canada there are no official restrictions.
Regarding your idea of an DTV visa: Ask your boss to rewrite the contract. Should not be a problem in your situation.
Or if you earn enough and the company is big enough, consider an LTR visa (smart visa).
Also, except for the accumulating expenses: you can get an multiple entry tourist visa, which gives you roughly 9 month in one go (how ever you have to border bounce, as each entry is only 60 days - which is the same as visa exempt - and can be extended by 30 days.)
Border bouncing is not bad anyway. Laos is a nice country. You can fly to Vietnam for 3 weeks too, or go to Cambodia.
Or do a "soft skills" DTV visa, learn a martial art, cooking or Thai Language.