To my knowledge it's now equivalent to $50,000 (around 1.7 million baht) you need to give a statement in the bank. It might actually be a benefit to do it and keep the receipt from Bank of Thailand, as you will be eligfible to later transferring same amount out of Thailand. I've for example done it with fund for my house construction.
You might also need a declaration when transferring out of your UK home country (I don't know the UK limit, but other European countries have limits).
Otherwise you can do two or more transfers separated by some weeks, as you suggest yourself.
Check the cost and exchange rate with your own bank and compare with Wise. Normally it's advised to transfer into to Thailand in foreign funds and let the receiving Thai bank do the currency exchange, but your own bank's rate might give you an idea when comparing to Wise.
Be aware of the 2024 income tax rules, if you stay in Thailand more than 180 days in the calendar year. You need to be able to prove that the 2 million baht is savings from before 1st January 2024, as they otherwise will be income taxed in Thailand.