You can use Grab, Bolt or InDrive. Compare prices in all 3 apps. Can vary by over 30%. Or just use a metered taxi from the airport's official queue system. Highly organised and easy.
Many people have suggested one of the onward ticket sites. Just be aware that every onward ticketing site only makes an on-hold reservation that shows as pending, not an actual paid ticket with an e-ticket number. This means there is always a chance that a knowledgeable person reviewing your proof of onward travel will know it isn't a valid ticket and is nothing more than a hold. You could actually do the same thing yourself by booking a flight on any airline website that allows a ticket hold for a few days or that allows a ticket hold to pay at the counter or at a store. It would generate the same reservation with a valid PNR booking code pending your payment. If you are using it at an airline check-in counter when they ask for an onward ticket, the check-in staff usually knows to look for an actual e-ticket number as PNR codes don't indicate it is an actual ticket. Onward ticket sites work well when applying for visas where consulate officers typically don't know the difference, but it is risky using it at an airport check-in counter when you have a one way ticket.
OK folks, for all of you answering, I can tell many of you don't know what an eSIM is, and are answering for old fashioned physical SIM cards. Please look up eSIMs as it is not the same thing. New high end phones support eSIMs where you download a virtual SIM rather than change physical SIM cards. Some phones like iPhone 14s and 15s sold in the USA don't even have physical SIM card slots any more and require you use eSIM.
you must not know what an eSIM is eSIM is not a physical SIM card New high end phones like iPhones now use eSIMs which are virtual software-based SIMs embedded into the device that do not use actual SIM cards. You download the information from the carrier to activate service rather than stick in a new SIM card. 7-11 definitely doesn't sell eSIMs.
Like every country, Thailand has different visa requirements depending on what passport you are using and how long you are staying. No one can tell you since you didn't mention your nationality. Please add that info.