Do I need to show an onward flight ticket when entering Thailand for 4 months with a return ticket?

You should have consulted the Thai Embassy before buying the ticket, you may get in trouble, if trying to stay more than 60 + 30 days visa exempt.

It changes every week in Thailand.. so the week before you plan on going contact a local travel agent or website! That’s a reason I will never return after visiting for many yrs

Depends on your airline, ask them.

You require a ticket out if Thailand before the end of your first visa .

It's the airline that checks in departure ,maybe ,maybe not

Go to

You can book an onward ticket for a few dollars.

Not a genuine ticket but accepted by immigration and initial airline.

Your plan will work with your onward ticket and you should have no Immigration issues unless you have a recent history of Visa Exempt entries especially if you took the 30 day extension.

If you are entering thailand on visa exempt, 60 days or a tourist visa 60 days then normally it is your flight ✈️ conpany that want to see an onward ticket flight or train etc. Out of thailand as its there responsibility if the thai authorities dont allow you to enter to return you to your departing country. So suggest you check with the flight company. The thai authorities dont normally look to see your return ticket although can ask if they want to. If you arrive on a non O visa then you dont need to show onward travel as its deemed a long term visa rather than a tourist visa