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

When entering Thailand on a visa-exempt status or a tourist visa (both valid for 60 days), it's generally advisable to have an onward ticket, as the airline may require it to ensure compliance with immigration laws. The Thai authorities may not actively check for your return ticket, but they can ask about it. If you're entering on a Non-O visa, you are not required to show onward travel documentation. It is also suggested to confirm with your airline about their policies, as these can vary. Some travelers recommend purchasing a cheap onward ticket if needed, but remember that regulations can change, so it's best to check closer to your travel date.