Thailand only has 2 cellphone companies. Both offer good quality at affordable prices. Take all 2, it will set you back 20 USD/EUR or any if you only have 10, there's no real difference.
Download their Apps, they offer attractive SEA roaming packages, no need to bother with new local providers again and again
well, the Embassy is free to reject such an application for technical violation. That's their right. If they approve it anyway, the lapse is cured I think. But yes, you are on the safest side of always following rules to the letter.
I understand your reasoning, but sometimes it's not possible to follow the rule for time constraints and Embassy processing duration between arriving in your home country and departing again.
You don't need to be in your country at the time of applying. However, you need to depart from your home country for the (even connecting)flight that uses the visa.
As verified by checking your boarding pass and your passport stamps.
I don't understand the reason for the rule, but they enforce it strictly.