challenge

for such courses as CELTA held in Thailand

you have to redraft the course to allow you to teach Thais just the phonetics of all the troublesome phonemes - any grammar you teach is just as a vehicle for the phonetics*

you also have to design in some sessions of one on one (ideally on selected and student-targeted phonemes - note you can use the students who get it right early to help you teach - has a snowball effect)

for the extra keen:

The one on one sessions would ideally be in front of an already accepted video camera so that you can capture perfect examples from students so that they can see themselves with perfect delivery

that can take time but the right video app will make it easier - you choose - there are many now (just have to allow you to mark a clip with a score on the fly - eg a star

(one day an app will use video and sound to recognise phonemes and tell you what they think you intended

soon probably)

)

pop

*the reason for this is that Thais get a LOT of grammar and vocabulary instruction - so the course could focus on what your devout students really need and what will benefit all others enormously