I have lived in Thailand for a long-time with my family and long-term Thai resident and fluent in Thai language. Definitely know about Thailand and its history more than you staying in London, UK. One of the or the best industry of Thailand is tourism bringing billions of dollars every year. If no tourism or foreigners Thailand would be poor like Laos, Cambodia or Myanmar.
It does. Your bra. in just doesn't get it that where did Thais and Siamese come from/ their ethnicities? There are many foreigners who became Thai citizens or PR holders. Some are not good enough so you do Visa extensions until end of your life.
Thailand completely exists because of foreigners. Even majority of Thais or Siamese are Chinese or Indian decent. Or from surrounding countries. Read some Thai history even recently from 100 or 50 years ago until now to understand about Thailand.
So you should try to remove yourself from the blacklist. I don't know for sure but I think should contact the embassy or immigration bureau and airport immigration to cancel the blacklist. I heard some did it by getting a lawyer. Or wait until the ban is finished.
I would just leave the country and not cancel anything. It gets cancelled when leaving. Or it depends if you want to stay in Thailand then can get a border run or return to your own country.
Edit: If you have multiple re-entry permit it seems you need to cancel the Visa at Bangkok immigration before leaving.