1. As many times as you want 2. There is no written maximum stay. But, if you're living the majority of the time in Thailand with only tourist visas or visa exemption there is a good chance you will eventually get questioned and possibly denied entrance by immigration. All it takes is one immigration officer having a bad day.
Agree with Brandon but I really do think you should look into a more long term visa (possibly elite) since you probably can't keep doing this indefinitely.
sorry didn't see that. I'm pretty sure you can get voa for Lao and Cambodia and get an evisa for Vietnam. Singapore I don't think you need a visa. Not sure about Malaysia. But I doubt you'll have any difficulties traveling to any country being a Portuguese passport holder.
I hear you sir, I personally had a very bad experience with immigration which was no fault of my own several years back and have used an agent ever since. The money really doesn't mean anything to me due to the convenience and lack of any stress. But to each their own. 😀