yes U have to get permission to leave for me it was no problem as I've spent most of the last 10 years in Thailand. The email sent to me said allowed to leave as leaving for more than 3 months so I think if U get 90 day or STV visa U should be ok
yes U can but if caught drinking it U would be in trouble maybe make U restart your 15 nights, I have a litre of whiskey in my bag but not going to risk being caught, I'm on my 3 Rd day of quarantine now