Sounds like you're overthinking it. The standard answer you'll get from any of the thousands of people doing what you're considering doing is "what, I need a v

Sounds like you're overthinking it. The standard answer you'll get from any of the thousands of people doing what you're considering doing is "what, I need a visa for this?" Nobody cares that you're working from your laptop without the correct visa. It's so vanishingly rare that anybody gets in trouble doing so that you'll find the one and only example in the archives here if you search (because it was so bizarre as to be news-worthy). Go back to that same internet cafe in Chiang Mai today and you'll be fine though. Just go as a tourist, and don't overstay. And have fun!