Hello sorry for what must be a frequently asked topic. I tried Google but couldn't find any info. I used to work in Bangkok but my school took care of everything visa related.  

  

I'm planning on visiting for 2 months, by arriving on a visa exemption for 30 days, and then getting a 30 day extension.  

  

It seems straightforward, and I understand Thai immigration will not have a problem.  

  

But my question is about the airlines onward flight requirements. Will they still want to see an onward flight within the initial visa-exempt 30 day timeframe?  It will be a big waste of money if I have to buy a flight I'll never use. Or will they accept the "assumed" extension?

The airline can still ask for a flight out of the within 30 day on arrival. A oneway ticket to a nearby country will be accepted.

You could get a single entry tourist visa before starting your trip that would allow a 60 day entry. No need for the onward ticket or a 30 day extension.

In case you are not clear, the potential issue is with the airline, not Thai immigration. There is no absolute answer to your question. Some airline employees may forget to check (especially if they are busy). If they do check, maybe they will not care about the date of the onward flight. If they are strict, they will require an onward flight within 30 days. Although the extension is routinely given in practice, it is supposedly only given at the discretion of the immigration official. The extension was originally intended only for exceptional situations where someone's travel plans had changed for some reason.

 

As a practical matter, in the past I have several times traveled to Thailand without visa or onward flight booking. When queried, I have always been able to convince the airline supervisor to check me in, assuring them that I know there will not be an issue with immigration. Sometimes, I needed to sign an indemnity form. Since the indemnity is of no value to the airline if you are not financially solvent, your appearance will sometimes be important as to whether you are able to talk your way on without an onward flight ticket. My sense is that airlines are becoming stricter on this.

 

If you are of a nervous disposition, simply get a single entry tourist visa. It is cheaper than the extension anyway.

get a tourist visa, almost the same price as a local extension , saves messing about whilst in Thailand, and you will avoid any possible tm28, tm30 problems.