it must say Thailand and preferably mention that you will not engage in any business with Thai people or companies. They want to see these points in writing no matter how redundant it appears.
Familiarize yourself with the e-visa application website, you can do a dummy application and not submit, it will expire in 14days, there are different upload sections, definitely only 1 PDF per relevant section. Quadruple check everything especially the passport biodata upload as the OCR scanner produces errors.
No need to buy a visa, you are eligible for a free 60 day visa exempt entry stamp. The only thing you need to do in advance is fill out the free TDAC arrival form online. Only fill in the starred items.