does your current phone not support dual sim ? Get an ESIM here in Thailand and you can turn on and off your UK sim as needed to run local data at much cheaper rate.
just a word of caution as not all transfers show as international transfers as required by Immigration. krungthai bank only shows international transfer when it’s bank to bank transfer. Example WU offers debit card payment and Thai debit card receive, that option does not show as international transfer and they can’t offer the bank letter needed by immigration.
Wise has a tool to check rates and charges to compare other transfer services. I check it often but use Western Union and don’t have issues with sending more than 50,000 to Krungthai
Agents can help a lot with navigating the opening bank account and starting your non-imm O package. They can help ensure you have all the paperwork in order and reduce your visits to immigration to 1 day each time you go.
Apply for a 60 day tourist visa (e-visa) and start your process as soon as you get here. In that time you need to get the bank account started and funded. Get a 30 day extension to your tourist e-visa as your next step. 15 days before your 30 day extension ends you need to be at immigration applying for Non-Imm O. Make sure you have at least 15 days remaining on your current visa or extension. Would not recommend waiting for exactly 15 days as holidays and other obstacles can appear.