@Luit ****************
I feel like this subject is similar to beating a dead horse.
The airline has told me " no problem with one way ticket " after all they * sold * me the ticket.
Yes I agree there is a risk with Thai immigration however I found nothing on the official Thai website about this.
To be crystal clear my intention is not to overstay but to further visit Vietnam, Malaysia, P I ,Indonesia.
If you know where on the Thai website it says must have proof of onward flight please share so I can comply.