the only reason you could get denied is if you try to apply for a teaching job (that drug arrest would matter) otherwise it won't affect getting a tourist visa
it's not easy to find a decent paid teaching job. you might end up with schools paying 1000us$/month. Korea pays the best, vietnam surely pays better than thailand
they just wanna make sure u are a legit tourist. I got a tourist visa the other month, went straight to the embassy in the morning, no questions asked and got it back a few hours later.
this is NOT correct. The officers at the airport can refuse you to get in even you've gotten a visa. Having a visa doesn't guarantee you can get in the country. (His visa application got denied, that should sound like a red flag)
I disagree with you, that might be the main issue. If you have a history of multiple tourist visas and several months spent in thailand each year, they might refuse it like they've done just one