My friend stayed in Thailand for 5 years on tourist visas and covid extensios. Occasionally they pull him aside and tell him that next time he can't come in... He always bring the 3 proofs. At landborders they usually don't pull him aside.
To Ho chi minh usually are cheap flights and getting a thai visa there is easy and quick if you have all documents ready. The cost of staying in Ho Chi Minh is similar to Bangkok.
I prefer going to ho chi minh, if there is a cheap flight available and if you can get a visa exemption for Vietnam. In Laos I prefer savanakhet because you don’t need to be in a big ass line
I did have to show that, they will check it there at the counter, they circle/underline the dates of the airplane tickets and booking and the balance of your account. But I need to say that I cancelled my booking from the hotel before I arrived there so they don’t do a deep check it seems.