Keep your stay to under 30 days then you'll have no need for a Visa. You'll probably get a terrible rate buying THB in Sweden so better that you purchase it when you get here, there are some great places like SuperRich in the Basement at BKK Airport where the rate is almost as good as you can get anywhere. Whichever way you decide to go, make sure you bring at least the equivelant of 20,000 (If travelling alone, 40,000 if travelling as a family) in cash which Google says is approx 7 (or 14,000 Swedish Krona) but I've just checked on TT https://ttexchange.com/ & the actual rate you'll get looks pretty awful (2.55 SEK to 1THB) so bring 8,000 (or 16,000) SEK, might even be worth Buying USD in Sweden then exchanging that here. SIM Cards can be bought at the airport or in most 7/11s / Tops, no problem with using ESIMs but I wouldn't have thought these would be a Thai SIM from somebody like AIS as these need to be registered against your passport.