In my experience, anything over 50,000 THB takes longer and this is reflected in Wise' calculator. It has been this way for some time now.
How the transaction is funded also affects the process. Wise website shows the following. First image is for a transfer of 49,999 THB and second for 50,000 THB or approx 1,424 Euro currently. From some of the comments on here I suspect they are using funds already in Wise and not the full process of home bank to Wise to Thai bank.