It all depends on your airline if they'll let you board from your departure country.
This is the issue. If you arrive here and you are declined entry at immigration who pays for the flight out of here? The airline that flew you here then has to cover the cost to fly you back. The airline can also get fined for allowing you to fly here without a return or onward flight.
So, if you do come here and are denied entry (very unlikely) you're not sat in the immigration detention centre waiting for someone to buy you a ticket out of here.
So, if you already have a return or onward flight you go on that at no cost to the airline.
Im from the UK but i returned here 2 weeks ago on a one way ticket from Frankfurt however, I have a Non O visa and a flawless 22 year immigration record.
I broke my femur in Pattaya 22 years ago and the lovely people at the Pattaya Memorial hospital gave me a free pair after they plated and screwed my femur back together.