IMHE there are two factors that usually determine the time taken for a WISE transfer.
Firstly, are the funds paying for the transfer held in a WISE account? If so, WISE do not need to wait for payment and the transfer will normally be instantaneous. Exceptions - I have experienced delays of up to 24 hours in this situation, once because of a long Thai holiday weekend, and another time the amount was THB5M. In the latter case I suspected it was the WISE agent in Thailand having to rearrange his cashflows.
I hold multi currencies in WISE and buy (or sell) within WISE as convenient. Usually all my transfers to Thailand arrive immediately because I'm transferring my own THB that is already paid for.
Secondly, if you buy THB in WISE and pay them from your domestic bank account, you are exposed to the banking interchange system of your own country. This can result in some delays for your payment to get to WISE as every country has a different interchange system that initiates the payment.
Most countries will be instantaneous with some variations for weekends and holidays depending on their interchange rules.
But if your domestic "bank" is not a real bank but something like a Building Society or a Co-Operative bank, you may have delays. Often (usually) these organisations are not part of centralised (automated) interbank interchange and do not have SWIFT. They may do manual interchange only once per day, (and probably at the end of the day) by instructing their bank to pay WISE.
Almost every time I come across someone complaining about WISE delays, their "bank" is something like The Wickersley Working Mens Building Society, or the Cleveland Savings and Loan Co-operative (names made up).