You should really check the double-tax avoidance agreement between your country and Thailand, and consult the tax office in the country where you currently pay taxes. There are different treaties and different rules. And not all treaties rely on the 180-day-rule. And not all income is taxed in the same way according to these treaties. As an example, in the Polish-Thai treaty, it states that you could be living in two countries and it's not the time you spend in these countries that matters but the ties you have with a given country or your nationality if you have equally strong ties with each of the countries. While you might have to file a tax return in Thailand, there is no one rule for everyone here where to pay taxes.
I had it with me when I did my 90-day check. The immigration complained that the landlord hadn’t uploaded the ownership deed along the TM30 and asked me to contact them next time or I won’t be allowed to do another check-in. If you’re renting a condo, then it’s best to bring both documents with you. If you’re staying in a hotel, simply ask reception for the document. The immigration was also pretty particular about the correctness of the address on TM47.
I bought a yearly SIM card... I used to come to Thailand and buy these 30-day SIM cards each time until they told me they had one that lasted for a year with a lot of Internet. It was a bargain at the price of 1790 BAHT with 100 GB Internet at full speed each month for a year.
Around 7 business days, almost 3 weeks, because it happened during different holidays in Thailand and Poland. It’s worth noting that embassies observe holidays in both countries.