ATM and always chose “not to apply exchange” allowing Visa and Mastercard use theirs. I guarantee you it will be always best rate and less risky than carrying cash.
The transaction fees and exchange rate of WU are crazy … not suitable for large and regular transfers. Ok for ad- hoc one -off transfer and even then Ria is much cheaper and on same principle.
not on the UK website - must be held in Baht in a Thai account which is a lot of money for just sitting there in addition to transaction and conversion costs.