appears to be a lot of comments here than can lead to confusion. Yes you are allowed to come here and work remotely. As in fact if the work and client are abroad and you are paid abroad then you are not functioning as a person working in Thailand. There thousands of business visitors coming every month these people are illegal? how silly. From some of the comments here are basically saying here that if you are here on holiday here and write email it’s illegaal. ??
yes on several occasions. never been asked. about 50% i have an exit ticket and the other 50% of the time not. Just explain to them that you don’t know when you will return
yes many times and never been asked. it depends on which country your flying from . From posts Australian and North American airlines seam to ask frequently