@Kevin ********
I'm a CMX girl so I'm not too sure about BKK.
I do know ProLanguage, if you want to do a language ED visa, is amazing.
In BKK it seems to be totally possible to do the conversions in country๐
But if you find an agent before processing your TR visa, it might just be worth asking them what's happening with the conversions and if you can apply before entering Thailand... Just a suggestion. And just to see what they say.๐๐
Good luck!!!