Question 1 you can transfer money from your UK account without paying any fees in the UK HSBC Bank FirstDirect Bank I think all banks allow you to do this I would always transfer ££ so it’s converted into ฿ when it arrives in Thailand
Any UK social payments like pensions can be paid into a Thai account but that would be unwise as any future pension increases will not be paid to you check it out on the gov webpage
I’ve been Transferring money from my UK account for the past 10 years and I’ve never had a problem
My only advice is if it’s your first time only transfer a small amount of money to begin with and once you know the money has arrived then there’s no reason why you can not send more
Once you open a bank account in Thailand you can send directly from your UK account free of any fees to your Thai account you will need the SWIFT Code and account number