Always a good idea to print everything out like Brandon said but I’ve never been asked to show anything but my passport and visa in over 15 years of going to Thailand.
That said, the current immigration management has changed things quite a bit and any immigration officer can decide to ask questions so best to print it out and bring it just in case.
If you can afford to jump through the hoops and really research your long term options and who you deal with to get long term visas (staying away from the many scams and sketchy visas that can come back to bite you), it’s really not that big of a deal.
The Thais you deal with day to day 99%+ of the time are fine with foreigners as long as you don’t act like a fool.
But the government is always looking for new ways to get more money out of foreigners and making it more difficult or expensive to stay long term.
Moving for how long? What’s the smallest condo you’re willing to live in? Do you cook at home a lot or eat out a lot? You planning on buying health insurance? You going to rent a motorbike or car or take taxis everywhere? What city you going to live in? You planning on traveling around a lot or partying every weekend or do you mostly do cheap/free things for fun? What visa will you be on?
The answers to these questions will impact your cost of living the most and you’ll want to figure them out to have a good idea of how much you need.
Research the cost of these things and set a realistic estimate for each, don’t assume you’ll be on the lower side, assume higher.
Then take that and add 15% to be safe.
Set a budget, track your spending with an app and stick to it and you should be good.
Have the funds ready to buy an emergency ticket out or cover significant medical costs if you don’t have good insurance and you’ll have set yourself up financially better than 90% of people who move to Thailand