@Bob *********
there is no guarantee an airline will accept a bus ticket for an onward travel proof, because they could say that the bus will only get you to the border but not across it 😃 The only safe and 100% guaranteed onward travel proof is a "real" cheap one way ticket out of Thailand. You can use Air Asia from Hat Yai to Kuala Lumpur as a perfect proof. Why do we hear about "onwardtickets" soon to get refused? Because they are not "real" flights but just reservations, one can clearly sort them out in the TIMATIC system, and since the beginning of the year the fine for violating IATA rules has risen five-fold, it can be up to 10.000.- USD per case.