A SWIFT first-party international wire transfer of USD directly to your account at Bangkok Bank in Thailand may be the best all-around option.
But you need to check with Vanguard (or Fidelity, TRowe, Citi etc.) to see what their procedures and costs are.
WISE may also be an alternative.
I know that Fidelity offers fee-free SWIFT transfers, BUT you need to have a Medallion-endorsed transfer order on file, and you need to call in the transfer. For me, I was required to submit this standing order in person at a Fidelity branch.
Transfers flow from Fidelity to Chase JP Morgan (intermediary bank, no fee) and on to BBL/THL, where they offer the TT Buying Rate and a sliding fee of between 200 and 500 THB.
https://aseannow.com/topic/1271424-usa-vanguard-wire-transfer-to-bangkok-bank/