Last time I entered Thailand all SETV applications had to be processed in your home country and I think there was some uncertainty about the CoE and whether people travelling from a third country were supposed to get it locally or from their home country.

 

A lot has changed since then - what's the score these days?

Often, a Thai embassy/consulate will only agree to issue you with a visa if you are a national or resident of the country where you are making the application. If you are temporarily in a country where the embassy has this rule, and are not eligible for a visa exempt entry, then you can be in an awkward spot.

 

Regardless, the CoE must be issued by the Thai embassy in the country you are departing to travel to Thailand. The embassy should be willing to process your CoE regardless of their visa policies.

Flew in from US to London on AU passport Started COE process in London All fine now in Phuket 

Some countries you transfer through may need proof of vaccine or tested negative.