Play safe and get a cheap onward ticket with Air Asia or similar or a bus ticket to a neighbouring country. It is the airline that can stop you boarding. Also complete your TDAC within 3 days of arrival, no more than 3 days. It is free so ensure you use the government website.
You will get 60 days visa exemption. Just make sure you have a return/onward ticked and fill in your TDAC online within (not more) than 3 days before arrival.
The airline will likely ask for a return/onward ticket. You can also book a cheap bus ticket to a neighbouring country. I was always asked for it when departing from Paris to Bangkok.