Do they accept Mir cards in Bangkok and can I withdraw money?

No, Mir cards are of course not accepted in Bangkok, and you cannot withdraw money either. Mir cards, due to sanctions, do not work almost anywhere in the world except for a few countries, but Thailand is not among them. Therefore, in Bangkok and anywhere in Thailand, you cannot pay with a Mir card or withdraw money from it. Read more about everything you need to know about currencies, money and plastic cards in Thailand here - https://nashaplaneta.net/asia/thai/valuta-dengi-v-tailande

Where to go in Thailand for the first time?
Do I need a category "A" license to rent a motorbike?
Can I exchange rubles in Phuket?
Follow the link, all these questions are discussed in the chat - https://t.me/thailand_travel_chat